In the beginning both Looney Tunes and Merrie Melodies drew their storylines from Warner's vast music library. From 1934 to 1943, Merrie Melodies were produced in color and Looney Tunes in black and white. After 1943, however, both series were produced in color and became virtually indistinguishable, with the only stylistic difference being in the variation between the opening theme music and titles. Both series also made use of the various Warner Bros. cartoon characters. By 1937, the theme music for Looney Tunes was "The Merry-Go-Round Broke Down" by Cliff Friend and Dave Franklin; the theme music for Merrie Melodies was an adaptation of "Merrily We Roll Along" by Charles Tobias, Murray Mencher and Eddie Cantor.

1930-1969

In 1929, WB became interested in developing a series of musical animated shorts to promote their music. They had recently acquired the ownership of Brunswick Records along with four music publishers for US $28 million. Consequently, they were eager to start promoting this material to cash in on the sales of sheet music and phonograph records. Warner made a deal with Leon Schlesinger to produce cartoons for WB. Schlesinger hired Rudolph Ising and Hugh Harman to produce their first series of cartoons. Bosko was Looney Tunes' first major lead character, debuting in the short Bosko, The Talk-Ink Kid in 1929. The first Looney Tunes short was Sinkin' in the Bathtub which was released in 1930.

When Harman and Ising left Warner Bros. in 1933 over a budget dispute with Schlesinger, they took with them all the rights of the characters and cartoons which they had created. A new character called Buddy became the only star of the Looney Tunes series for a couple of years. New directors including Tex Avery, Friz Freleng and Bob Clampett were brought in to work with animators in the Termite Terrace studio. In 1935 they debuted the first truly major Looney Tunes star, Porky Pig, along with Beans the Cat in the Merrie Melodie cartoon I Haven't Got a Hat directed by Friz Freleng. Beans was the star of the next Porky/Beans cartoon Golddiggers of '49, but it was Porky who emerged as the star instead of Beans. The ensemble characters of I Haven't Got a Hat, such as Oliver Owl, and twin dogs Ham and Ex, were also given a sampling of shorts, but demand for these characters was far exceeded by Beans and Porky; Beans himself was later phased out due to declining popularity, leaving Porky as the only star of the Schlesinger studio. This was soon followed by the debuts of other memorable Looney Tunes stars; Daffy Duck (in 1937's Porky's Duck Hunt), Elmer Fudd (in 1940's Elmer's Candid Camera) and Bugs Bunny (in 1940's A Wild Hare).

Bugs initially starred in the color Merrie Melodies shorts and formally joined the Looney Tunes series with the release of Buckaroo Bugs in 1944. Schlesinger began to phase in the production of color Looney Tunes with the 1942 cartoon The Hep Cat. The final black-and-white Looney Tunes short was Puss n' Booty in 1943 directed by Frank Tashlin. The inspiration for the changeover was Warner's decision to re-release only the color cartoons in the Blue Ribbon Classics series of Merrie Melodies. Bugs made a cameo appearance in 1942 in the Avery/Clampett cartoon Crazy Cruise and also at the end of the Frank Tashlin 1943 cartoon Porky Pig's Feat which marked Bugs' only appearance in a black-and-white Looney Tunes short. Schlesinger sold his interest in the cartoon studio in 1944 to Warner Bros. and went into retirement; he would die five years later. As the 1940s and 50s ran on, many more popular characters in the Looney Tunes and Merrie Melodies series were introduced and added to the roster, including Tweety, Sylvester, Granny, Yosemite Sam, Foghorn Leghorn, Marvin the Martian, Pepé Le Pew, Speedy Gonzalez, the Tasmanian Devil, Wile E. Coyote and the Road Runner.

The original Looney Tunes theatrical series ran from 1930 to 1969 (the last short being Bugged By A Bee, by Robert McKimson). During part of the 1960s, the shorts were produced by DePatie-Freleng Enterprises after Warner Bros. shut down their animation studios. The shorts from this era can be identified by their different title sequence, featuring stylized limited animation and graphics on a black background and a new arrangement, by William Lava, of "The Merry-Go-Round Broke Down". The change in the introductory title cards was possibly to reflect the switch in the animation style of the shorts themselves. Another noticeable difference in these shorts was the absence of Bugs, Tweety and several other starring characters, while Daffy, Speedy, the Coyote and the Road Runner continued to be featured prominently.

1970-1999

The Looney Tunes series' popularity was strengthened even more when the shorts began airing on network and syndicated television in the 1950s under various titles and formats. However, since the syndicated shorts' target audience was children and because of concerns over children's television in the 1970s, the Looney Tunes shorts were edited, removing scenes of violence (particularly suicidal gags and scenes of characters doing dangerous stunts that impressionable viewers could easily imitate), racial and ethnic caricatures (particularly stereotypical portrayals of blacks, Mexicans, Jews, Native Americans, Asians, and Germans as Nazis) and questionable vices (such as smoking cigarettes, ingesting pills, and drinking alcohol).

Theatrical animated shorts went dormant until 1988 when new shorts were made to introduce Looney Tunes to a new generation of audiences. New Looney Tunes shorts have been produced and released sporadically for theaters since then, usually as promotional tie-ins with various family movies produced by Warner Bros. While many of them have been released in limited releases theatrically for Academy Award consideration, only a few have gotten theatrical releases with movies. The last series of new shorts so far ended production in 2004, the most recently theatrically released Looney Tunes was Pullet Surprise in 1997, shown theatrically with Cats Don't Dance.

In the 1970s through the early 1990s, several feature-film compilations and television specials were produced, mostly centering on Bugs Bunny or Daffy Duck, with a mixture of new and old footage. In 1976, the Looney Tunes characters made their way into the amusement business when they became the mascots for the two Marriott's Great America theme parks (Gurnee, Santa Clara). After the Gurnee park was sold to Six Flags, they also claimed the rights to use the characters at the other Six Flags parks, which they continue to do presently. In 1988, several Looney Tunes characters appeared in cameo roles in Touchstone, Disney and Amblin's Oscar-winning epic, Who Framed Roger Rabbit. The more notable cameos featured Bugs Bunny, Daffy Duck, Porky Pig, Yosemite Sam, Sylvester, and Tweety. It is the only time in which Looney Tunes characters have shared screen time with their rivals at Disney (producers of the film)—particularly in the scenes where Bugs Bunny and Mickey Mouse are skydiving, and when Daffy Duck and Donald Duck are performing their "Dueling Pianos" sequence.

In 1988, Nickelodeon aired all the unaired cartoons in a show called Looney Tunes on Nickelodeon until 1999. To date, Looney Tunes on Nickelodeon is the longest-airing animated series on the network that was not a Nicktoon. In 1996, Space Jam, a feature film mixing animation and live-action, was released to theaters starring Bugs Bunny and basketball player Michael Jordan. Despite its odd plot and mixed critical reception, the film was a major box-office success, grossing nearly $100,000,000 in the U.S. alone, almost becoming the first non-Disney animated film to achieve that feat. For a two-year period, it was the highest grossing non-Disney animated film ever. The film also introduced the character Lola Bunny, who subsequently became another recurring member of the Looney Tunes, usually as a love interest for Bugs.

In 1990, computer colorized cartoons released from 1936 to 1943 were released under Warner Bros..

Since the days of the Nintendo Entertainment System, the Looney Tunes characters have been featured in numerous video games, such as a same-titled one that came out on Game Boy in 1992. It was later remade for the Game Boy Color in 1999; it was not a best seller and received poor reviews. The Looney Tunes characters have had more success in the area of television, with appearances in several originally produced series, including Taz-Mania (1991, starring the Tasmanian Devil), and The Sylvester and Tweety Mysteries (1995, starring Sylvester the Cat, Tweety Bird and Granny). The gang also made frequent cameos in the 1990 spinoff series Tiny Toon Adventures, from executive producer Steven Spielberg where they played teachers and mentors to a younger generation of cartoon characters (Buster, Babs and the gang), plus occasional cameos in the later Warner shows Animaniacs (also from Spielberg) and Histeria!.

2000-present

In 2000, WB decided to make the Looney Tunes and Merrie Melodies library exclusive to fellow Time Warner properties, specifically Cartoon Network. Immediately prior to this decision, Looney Tunes shorts were airing on several networks at once: on Cartoon Network, on Nickelodeon (as Looney Tunes on Nickelodeon), and on ABC (as The Bugs Bunny and Tweety Show). The latter two had been particularly long-running series, and the Warner Bros. decision forced the two networks to cancel the programs. In 2003, another feature film was released, this time in an attempt to recapture the spirit of the original shorts: the live-action/animated Looney Tunes: Back in Action. Although the film wasn't financially successful, it was met with relatively positive reviews from film critics, and has been argued by animation historians and fans as the finest original feature-length appearance for the cartoon characters. In 2006, Warner Home Video released a new, Christmas-themed Looney Tunes direct-to-video movie called Bah, Humduck! A Looney Tunes Christmas featuring a wide array of characters working in a mega-store under the Scrooge-esque Daffy Duck. The movie parodies the famous book by Charles Dickens, A Christmas Carol. Other Looney Tunes TV series included Baby Looney Tunes (2002, which had a similar premise to Muppet Babies), Duck Dodgers (2003, starring Daffy Duck, Porky Pig and Marvin the Martian) and Loonatics Unleashed, (2005, featuring futuristic versions of the characters).

Although the cartoons are seldom seen on mainstream TV, thanks to revival theatrical screenings, and the Golden Collection DVD box sets, the Looney Tunes and its characters have remained a part of Western animation heritage. On October 22, 2007, Looney Tunes and Merrie Melodies cartoons became available for the first time in High Definition via Microsoft's Xbox Live service, including some in Spanish. From February 29 – May 18, 2008, many Looney Tunes artifacts, including original animation cels and concept drawings, were on display at the Butler Institute of American Art in Youngstown, Ohio, just off the campus of Youngstown State University. The exhibit had the studio come full circle, as the Warners were natives of the Youngstown area. Looney Tunes can currently be seen on the Kids WB! website.Looney Tunes returned to Cartoon Network on January 1, 2009, as a marathon called the "New Year's Day Looney Toonormous Marathon", but did not air on Cartoon Network or Boomerang again until 11 months later when it returned to Cartoon Network on November 15, 2009. In 2010, Looney Tunes was taken off Cartoon Network after another New Year's Marathon.

At the Cartoon Network upfronts in April 2010, "The Looney Tunes Show" was announced to premiere in November 2010. However, the series peremiere was pushed back to February 2011, then it was pushed back again to May 2011. Coming from Warner Bros. Animation and producer Sam Register, the concept revolves around Bugs and Daffy leaving the woods and moving to the suburbs with "colorful neighbors" including Sylvester, Tweety, Granny, and of course Yosemite Sam. The show features 2-minute music videos titled respectfully "Merrie Melodies", as a tribute to the Looney Tunes sister shorts, which features the characters singing original songs. The Looney Tunes Show debuted May 3, 2011. At approximately the same time, reruns of the classic Looney Tunes library returned to Cartoon Network's daytime lineup.

Also, it has been announced that Wile E. Coyote and Road Runner will be making a return to the big screen in a series of 3-D shorts that will precede select Warner Bros. films. There are currently six in the works that began with the first short, Coyote Falls, that preceded the film Cats & Dogs: The Revenge of Kitty Galore, which was released on July 30, 2010. On December 17, 2010, Rabid Rider was precede the film, Yogi Bear. On June 8, 2011, Warner Bros. Animation announced that there will be more Looney Tunes 3-D theatrical shorts; the first titled Daffy Rhapsody with Daffy Duck and Elmer Fudd, the next being I Tawt I Taw a Putty Tat with Sylvester, Tweety and Granny. Daffy Rhapsody was to precede the film Happy Feet Two, until the studio decided to premiere I Tawt I Taw a Putty Tat instead. Daffy Rhapsody instead premiered in 2012, preceding Journey 2: The Mysterious Island.

On September 19, 2012, it was announced that a new Looney Tunes reboot film is in development. For­mer Saturday Night Live cast mem­ber Jenny Slate is already on board as writer for the new flick. Jef­frey Clif­ford, Harry Potter pro­ducer David Heyman and Dark Shadows writ­ers David Katzen­berg and Seth Grahame-Smith are slated to pro­duce the film.

When the Looney Tunes and Merrie Melodies began in 1930, although Warner Bros. retained the rights to the cartoons, Harman and Ising owned the rights to the Bosko characters. When Harman and Ising left Warner Bros. in 1933, their former producer Leon Schlesinger started his own studio for Warner Bros. continuing the Looney Tunes series. Harman and Ising retained the rights to Bosko and began making Bosko cartoons at Metro-Goldwyn-Meyer in 1935. However these cartoons were not a success and in 1937 MGM fired Harman and Ising and formed their own studio to create MGM cartoons, with Harman and Ising retaining the rights to Bosko. Time Warner eventually acquired the character from their estates. Meanwhile the Schlesinger studio continued to make popular cartoons until 1944 when Schlesinger sold his studio to Warner Bros. and since then, Warner Bros. has owned all rights to all post-1933 characters created by Leon Schlesinger Productions and Warner Bros. Cartoons. The rights to individual cartoons however are in other hands.

In 1955, Warner Bros. sold its black-and-white Looney Tunes (plus the black-and-white Merrie Melodies made after Harman and Ising left) into television syndication through their sale of the cartoons to Guild Films. The copyright to those cartoons were assigned to Sunset Productions. These cartoons were distributed by Guild Films until it went bankrupt and shut down in 1961. Warner Bros. then licensed the syndication rights to Seven Arts Associated, who distributed them until their purchase of Warner Bros. in 1967.

In 1956, Associated Artists Productions (a.a.p.) acquired for television most of Warner Bros' pre-1950 library, including all Merrie Melodies (except for those sold to Sunset and Lady, Play Your Mandolin!) and color Looney Tunes shorts that were released prior to August 1948. Unlike the sale to Sunset Productions, a.a.p. was allowed to keep the Warner titles intact and simply inserted an "Associated Artists Productions presents" title at the head of each reel (as a result, each Merrie Melodie cartoon had the song "Merrily We Roll Along" playing twice). a.a.p. was later sold to United Artists, who merged the company into its television division—United Artists Television.

In 1981, UA was sold to Metro-Goldwyn-Meyer, and five years later, Ted Turner acquired the pre-May 1986 MGM library—which included the rights to MGM's cartoon characters like Tom and Jerry and Bosko. He also acquired the rights to the a.a.p. library. In 1996, Turner's company, Turner Broadcasting System (whose Turner Entertainment division oversaw the film library), was purchased by Time Warner who also owned Warner Bros.. Today, Warner Home Video holds the video rights to the entire Looney Tunes/Merrie Melodies animated output by virtue of Time Warner's ownership of Turner Entertainment—this is why their Looney Tunes Golden Collection DVD box sets include cartoons from both the pre-8/48 Turner-owned and post-7/48 Warner Bros. owned periods. As of 2012, all Warner Bros' animated output are under the same Time Warner umbrella of ownership.

Starting in 1960, the cartoons were repackaged into several different TV programs that remained popular for several decades before being purchased by Turner Broadcasting Systems. Turner's Cartoon Network reran the cartoons for 12 years, from their start in 1992 until 2004, when the cartoons were removed from the schedule. In November 2009, Cartoon Network brought back reruns of Looney Tunes shorts. After only one month, the network stopped airing the cartoons on January 1, 2010. In March 2011, the cartoons returned once again to Cartoon Network, as a run-up for the new series The Looney Tunes Show.

A handful of Looney Tunes and Merrie Melodies shorts are no longer aired on American television nor are they available for sale by Warner Bros. because of the racial stereotypes of black people,Native Americans, Asians such as Japanese (especially during WWII, as in Tokio Jokio and Bugs Bunny Nips the Nips), Chinese and Germans included in some of the cartoons. Eleven cartoons that prominently featured stereotypical black characters (and a few passing jokes about Japanese people, as in Coal Black and de Sebben Dwarfs and Jungle Jitters) were withdrawn from distribution in 1968 and are known as the Censored Eleven.

In 1999 all Speedy Gonzales cartoons were banned because of their alleged stereotyping of Mexicans. When many Hispanics protested that they were not offended, and fondly remembered Speedy Gonzales cartoons as a representation of their youth and nation's individuality, these shorts were made available for broadcast again in 2002.

In addition to these most notorious cartoons, many Warner Bros. cartoons contain fleeting or sometimes extended gags that reference then-common racial or ethnic stereotypes. The release of the Looney Tunes Golden Collection: Volume 3 includes a disclaimer at the beginning of each DVD in the volume given by Whoopi Goldberg which explains that the cartoons are products of their time and contain racial and ethnic stereotypes that "were wrong then and they are wrong today", but the cartoons are going to be presented on the DVD uncut and uncensored because editing them would be the same as denying that the stereotypes existed.

A written disclaimer, similar to the words spoken by Goldberg in Volume 3, is shown at the beginning of each DVD in the Looney Tunes Golden Collection: Volume 4, Volume 5, and Volume 6 sets, as well as the Daffy Duck and Foghorn Leghorn Looney Tunes Super Stars sets:

The cartoons you are about to see are products of their time. They may depict some of the ethnic and racial prejudices that were commonplace in the U.S society. These depictions were wrong then and they are wrong today. While the following does not represent the Warner Bros. view of today's society, these cartoons are being presented as they were originally created, because to do otherwise would be the same as claiming that these prejudices never existed.

Inducted into the National Film Registry

• Porky in Wackyland (1938), selected in 2000

Academy Awards for Best Short Subject (Cartoon)

• For Scent-imental Reasons (1949)
• Knighty Knight Bugs (1958)

Academy Award nominations

• Greetings Bait (1943)
• Swooner Crooner (1944)
• Walky Talky Hawky (1946)
• Mouse Wreckers (1949)
• From A to Z-Z-Z-Z (1953)
• Sandy Claws (1955)
• Tabasco Road (1957)
• Mexicali Shmoes (1959)
• Mouse and Garden (1960)
• High Note (1960)
• Now Hear This (1963)

Television series

• The Bugs Bunny Show (1960-2000)
• The Road Runner Show (1966-1973)
• Tiny Toon Adventures (1990-1995)
• Taz-Mania (1991-1995)
• The Sylvester & Tweety Mysteries (1995-2002)
• Baby Looney Tunes (2002-2005)
• Duck Dodgers (2003-2005)
• Loonatics Unleashed (2005-2007)
• The Looney Tunes Show (2011–present)

Feature films

• The Bugs Bunny/Road Runner Movie (1979)
• The Looney Looney Looney Bugs Bunny Movie (1981)
• Bugs Bunny's 3rd Movie: 1001 Rabbit Tales (1982)
• Daffy Duck's Movie: Fantastic Island (1983)
• Daffy Duck's Quackbusters (1988)
• Space Jam (1996)
• Looney Tunes: Back in Action (2003)

Video games

• Merrie Melodies
• Warner Bros. Cartoons
• Warner Bros. Animation
• Looney Tunes and Merrie Melodies filmography
• List of Looney Tunes and Merrie Melodies characters