The series follows Max, an adventurous preteen boy who receives a package in the mail. The package contains a small statue of a fowl, inscribed with Egyptian hieroglyphs. The translation reveals a message that reads: "You have been chosen to be the cap-bearer. Go to the mini-mart and wait for a sign, Mighty Max." Shocked by the message, Max drops the statue, shattering it and revealing a red baseball cap emblazoned with a yellow "M", which he puts on.

Upon arriving at the mini-mart, he is chased by a lava-monster sent by Skullmaster, a megalomaniacal demon who lives within the earth and has the power to create evil minions. As Max races away, the cap activates a vortex that transports him instantly from his current location (somewhere in the United States), to the Mongolian desert, where Max is met by Virgil, a nearly omniscient Lemurian, whose appearance is that of an anthropomorphic "fowl" (a running gag in the series is that Max refers to Virgil as a "chicken" to which the Lemurian replies "Fowl, actually."). Virgil explains that Max's reception of the cap was prophesied c. 3000 BC. Max, Virgil, and Norman, his Viking bodyguard (he is three times larger than Max), travel together around the world, defending Earth against the minions of Skullmaster, who is responsible for the downfall of both the Lemurians and the people of Atlantis. Norman is supposedly immortal and has improvised being various legends, including Sir Lancelot, Thor, Samson, and Hercules, as first talked about in episode 5, "Let Sleeping Dragons Lie." Norman finds Thor's hammer and helm and uses them throughout the episode. When Max first sees him he asks, "You were Thor!?" and Virgil explains that to maintain the Cosmic Balance they had to call in outside help.

Most plot-driving episodes involve Skullmaster or one of his demons, but in many episodes, Max is required to intervene to stop an independent villain. While all episodes involve travel across Earth, one involves time travel, and the portal can even extend into the astral plane as seen in the episode "Souls of Talon".

While generally lighthearted and comical, the show's violence and descriptions of violent acts were considered graphic by some viewers. Many episodes began with a prologue of a person being killed by the episode's menace; while nothing graphic is shown, it was more grown up than most shows aimed at children.

The show's dark series finale featured Max, Norman, and Virgil pitted against Skullmaster and their previously defeated foes. Both Norman and Virgil are killed, leaving Max as the only one to defeat Skullmaster (who is about to gain ultimate power). In the final struggle, Max is unable to defeat Skullmaster, and instead of allowing him to conquer the world uses the cap to send time backwards to the events of the first episode, creating a time paradox. At first, he doesn't remember anything and experiences déjà vu, but after he reads Virgil's modified letter, he recalls everything, and decides to set it right in order to defeat the Skullmaster.

Heroes

• Max (voiced by Rob Paulsen) - Max is the main protagonist of the series. Max is a rambunctious young teenager who is very good at getting out of (and into) trouble. One day, he receives a mysterious package containing a videotape and a red baseball cap with a large, yellow "M" on it. The cap is actually an ancient key to various portals found throughout time and space, and as he soon finds out, Max has been chosen as its bearer and protector. Upon donning the cap, he becomes the Capbearer —the Mighty One. Max soon meets his Lemurian mentor Virgil, a 4-foot-tall creature resembling a chicken, and Norman, a ten-thousand year old Norse warrior who would serve as Max's bodyguard. Lastly, Max meets his arch-enemy Skullmaster, the evil warlord who killed the entire Lemurian race in search of the key. Now Max must protect the key and the portals from Skullmaster, as well as maintain balance in the world. This often means foiling alien plots, defeating evil in all forms, and generally having fun doing it. Max makes clear his reluctance to be the Mighty One, which only seems to get him into trouble and even greater danger. He would rather get on with being a normal everyday kid and play with his friends, but Virgil and the cap leave him with little choice.

• Virgil (voiced by Tony Jay) - Virgil is the last living Lemurian, and the next step in human evolution, as revealed in one episode. The Lemurians either created or discovered the portals, and later created the key in order to access them. Having a bird-like appearance, the Lemurians valued knowledge above all else and compiled the most extensive library the world has ever known. They were destroyed by Skullmaster in his quest for the key. Virgil is over ten thousand years old, and is very knowledgeable about both the past and future. However, the majority of his trust rests on his ancient texts, and he seems to lack compulsion. Virgil is always serious, and quite often frustrated by Max's carefree ways. What's more, though he looks like a talking chicken and is often referred to as such, he keeps insisting that he is actually a fowl. It should also be noted that Virgil was Skullmaster's teacher, and he is often reminded of this fact.

• Norman (voiced by Richard Moll) - Norman is Max's bodyguard. In the time of the early Vikings, a young Norman watched his father die at the hands of Spike, an indestructible deranged and bloodthirsty warrior. Because of his size at the time, Norman couldn't help when he had the chance (he was unable to lift his father's war-axe), and thus blamed himself for the tragedy; at his father's grave, he vowed to become the greatest warrior that ever lived (cf. "Norman's Conquest"). After a lifetime of battle, Norman was approached by Virgil to become the guardian. He earned his immortality by defeating the Conqueror, an undefeated champion, and swore to defend the Mighty One with his life if necessary (cf. "Dawn of the Conqueror"). As the Mighty One's bodyguard, Norman is usually serious, but unlike Virgil, he seems to enjoy Max's carefree ways. Norman's exploits through the ages were the basis of numerous legends, including Thor, Hercules, Samson, Lancelot, and Little John, presumably among others. Norman is shown throughout the series to be practically impervious to fear, though he is not above disgust. The only creatures that give him pause for terror are spiders. In the show he meets several of tremendous size and strength. It is in hinted in the final episode he may have finally met his match in combat and died at the eight hands of an enormous spider. His common catchphrase is, "I eat ____ for breakfast", usually following the introduction or emergence of the group's latest foe, such as, "I eat zombies for breakfast." Another is the wry statement made upon meeting one of the many monsters they encounter, "That is a big ____."

Allies

• Max's Mother (voiced by Tress MacNeille) - An archaeologist who works for the local museum. She often travels all over the world, and usually leaves Max to his own devices. She tries to be a good mom, and tends to worry about Max since finding out that he is the Mighty One. More than once Max has had to rescue her, as her love for archaeology sometimes overrides her better judgment. Despite her initial shock at seeing a talking chicken (fowl actually), she and Virgil often have historical discussions, and she is one of the few people who can out-talk the Lemurian.

• Bea (voiced by Kath Soucie) - Bea is one of Max's two best friends. Bea is an intelligent young girl who has assisted Max (and saved him) on more than one occasion. Level-headed and cool under pressure, she often balances Max's exuberance and impulsiveness with a more intellectual approach to problems. Bea has also expressed more than a passing romantic interest in the Mighty One (cf. "Snakes & Laddies"), which has yet to be reciprocated.

• Felix (voiced by Corey Burton) - Felix is Max's other best friend. Felix usually cares more about eating and having fun than saving the world. He takes Max's role as the Mighty One in stride, never letting it overshadow the fact that Max was his friend before he was the Capbearer. Felix has assisted Max on numerous occasions, but usually gets left behind when the adventure starts. He has always been dependable, though, and Max knows he can rely on Felix for help whenever he needs it.

• Thor - Thor is Max's pet green iguana and loyal companion. Thor has helped out Max on a couple of occasions. During Max's first encounter with Dr. Zygote, Thor was "de-evolved" into a dinosaur and ended up rescuing Max from Zygote's Tyrannosaurus rex-like "Mutosaurus" (cf. "Zygote's Rhythm"). After the good doctor's exit, Max evolved Thor back into his usual, pocket-sized self.

Villains

• Skullmaster (voiced by Tim Curry) - The primary antagonist of the series and the arch-nemesis of the Mighty One. Skullmaster is an ancient warrior/sorcerer whose lust for power has driven him to destroy at least two civilizations, the Lemurians and the Atlanteans. He destroyed the Lemurians out of wrath when they would not give him the secrets of the key and he used the souls of Atlantis to power his Crystal of Souls. At some point, Skullmaster was imprisoned deep within the earth where he sealed the reigning king Lava Lord into solid rock and took control of his minions. During the second season, Skullmaster is free to roam the earth and proceeds to cause all kinds of trouble.
  • Warmonger (voiced by Frank Welker) - Warmonger is a demon who is Skullmaster's right-hand man so to speak. The dimwitted Warmonger usually finds himself doing Skullmaster's dirty work, but also enjoys the positions of relative power this gives him over other minions. Cruel and sadistic, he briefly showed ambition when he tried to kill Skullmaster in the episode "I, Warmonger". Believing himself successful, Warmonger then found himself at a loss as to what to do with his new-found power and position. The death of Skullmaster proved to be a ruse however and Skullmaster was proud of his pupil for showing such deviousness.

• Arachnoid (voiced by René Auberjonois) - Dr. Stanley Kirby is a scientist who was mutated into the half-spider Arachnoid.

• Cyberskull (voiced by Danny Goldman) - Cyberskull is a programmer who merged with a computer virus and discovered that he can alter reality and become electricity. He plotted revenge on the founder of MegaCorp for stealing his ideas. He later returned to create a physical body for himself.

• Professor Eggbert Zygote (voiced by Kenneth Mars) - Eggbert Zygote is a mad scientist with plans to manipulate evolution. In his first appearance in "Zygote's Rhythm", he developed a machine that devolved reptilian life back to their dinosaur forms. In "Zygote Music", he captures a telepathic boy whom he believes to be the key to human evolution. He is "defeated" when he evolves to the infinite, no longer interested in such primal concepts like good and evil.

• Lava Lord (voiced by Frank Welker) - Lava Lord is the previous ruler of Underworld. Lava Lord was dethroned and sealed in solid rock by the more powerful Skullmaster. At the beginning of season 2, Lava Lord was freed as a side effect of Skullmaster's crystal of souls being destroyed at the end of season 1. His revival switched the allegiance of the Lava Beasts to him as he is their natural master. He planned to destroy Skullmaster with a giant robot called Magus that he was very proud of and treated like a son. Though he is technically evil and has no love for humans, his hatred for Skullmaster has caused him to align with Max on more than one occasion.
  • Lava Beasts - Creatures of molten rock that served Lava Lord. Skullmaster gained control of them after sealing away Lava Lord, yet returned to the services of Lava Lord after Max broke the Crystal of Souls.

• Corey Burton – Felix
• Tim Curry – Skullmaster, Jules Verne
• Tony Jay – Virgil
• Tress MacNeille – Max's Mother
• Richard Moll – Norman
• Rob Paulsen – Max
• Kath Soucie – Bea
• Frank Welker – Warmonger, Lava Lord

Additional voices

• Charlie Adler – Calimarus, Ernie, Football Coach
• René Auberjonois – Arachnoid, Nadja
• Michael Bell – Hydra (Good Side)
• Hamilton Camp –
• Glen Chin – Lao Chu/Ki Wan
• Jim Cummings – Beowulf, Conqueror, Doom Dragon, J. "Ollie" Oleander Pettybone, Ravendark
• Miriam Flynn – Professor MacDougal
• Brad Garrett – Spike
• Linda Gary – Kali
• Ellen Gerstell –
• Danny Goldman – Cyberskull
• Dorian Harewood –
• Michael Horse – Yana-Ya-In
• Charles Kimbrough – Dr. Robert Scorpio
• Clyde Kusatsu – Hanuman
• Katie Leigh –
• Victor Love –
• Kenneth Mars – Professor Eggbert Zygote
• Jason Marsden – Young Norman
• Kate Mulgrew – Isis
• Ron Perlman – Goar
• Henry Polic II – Nemo
• Roger Rees –
• Neil Ross – Hydra (Bad Side)
• Paula Tiso

Crew

VHS and DVD

Educational Epilogue

Merchandise==
The merchandising was far more popular than the show itself. Mighty Max toys were sold as play-sets of varying sizes with very small (usually non-articulated) figurines inside. Each play-set contained a Mighty Max figure as well as one or more villains and sometimes Virgil, Norman, or both. There were a small series of larger, more expensive play-sets with various mechanical and electronic features such as opening jaws (on an island play-set shaped as a dragon's head) and lights. Almost all episodes of the TV series were based at least loosely on one of the Mighty Max play-sets.

In 1995, due to the popularity of the play-sets at the time, the McDonald's Happy Meal offered a toy play-set featuring Mighty Max.

A video game, The Adventures of Mighty Max, was released for the SNES and Sega Genesis/Mega Drive (which were packaged with a VHS copy of Day of the Cyclops and Let Sleeping Dragons Lie, respectively). A handheld game was also released from Tiger Electronics and Systema.

The show generated other merchandise such as a comic book (10 issues), a sticker album, at least one puzzle, and board games. In some countries, replicas of Max's cap were sold, although not all are necessarily officially licensed merchandise.