Natsume version

Casper is a game developed by Absolute Entertainment and published by Natsume. The player controls Casper, followed by Kat Harvey whom he has to protect from any danger. Being a ghost, Casper can pass through walls and other obstacles, but he can't go away from Kat too much, or else Carrigan's ghost will abduct her. The game follows loosely the plot of the movie. This game uses a revised Absolute A Boy and His Blob engine. Picking up special objects allows Casper to morph into these objects to clear rooms of enemies, and to protect Kat from certain hazards. Mirrors placed throughout the game allows Casper and Kat travel to other parts of mansion, and outside electrical lines allow Casper to pick up the last of the toys, when he picks up the electric bolt morph.

KSS version

A different game, this time developed by Natsume, was released only in Japan by the anime company KSS. In this version, the game uses an isometric view and the player controls Kat Harvey herself as she protects Casper from a duo that consists of a male government agent and a female government agent. During the course of the game, Kat collects items, therefore making this game an adventure game as opposed to an action game.

Baseballs are used to stun the secret agents. Getting hit by a secret agent results in a game over. There is even a box to the bottom right that keeps track of time (in seconds and minutes); the game starts with ten seconds elapsed. Saving the game is as easy is finding mechanical contraptions and activating them. While saving the game, the game counts all the coins and gems; it uses that count to tabulate a percentage to decide how much of the game has been officially completed.

Interplay's version

The version published by Interplay plays as a top-view action-adventure game with pre-rendered graphics. The game consists of three acts, first finding tokens of friendship for Kat and Dr. Harvey, then finding the pieces for the Lazarus machine (which Casper's uncles had disassembled under the impression he would use it on himself), and finally finding the Cellular Integrator (which Carrigan's ghost steals, leading Casper to her lair) while exploring the mansion and dealing with the Ghostly Trio (especially in the second act, as Casper's uncles as well as different variants thereof [like Gravedigger Stretch, General Fatso and Hedgecutter Stinky] guard the pieces of the Lazarus). Unlike other versions, other than the Ghostly Trio and Carrigan (who serves as this version's final boss), there are no enemies. The game instead focuses on solving puzzles.

While playing through the game, it becomes apparent that certain areas of the game appear to be unlockable, and one certain puzzle (located within a library of sorts) has you basically flip switches until the solution presents itself, allowing entry into a room where you can obtain puzzle pieces that fit somewhere in the game. Using a cheat however, which enables you to float as high as you please, the player is able to explore a huge, hidden area of the mansion, where every morph, and every item needed to complete the game are to be found.