"Earthworm Jim 3D is to date the last console game in the Earthworm Jim series. Created by Interplay and based more on the Television series than the canon of the previous games, Earthworm Jim 3D was released for Nintendo 64 and PC. While the game featured classic villains such as Psy-Crow and Professor Monkey-For-A-Head, it was criticized for falsely advertising on the game box that Evil the Cat was included. This omission was due to a rushed development cycle, leading to the removal of a number of game locations (some also appearing on the game box) in an attempt to meet the game's release date. And as such, a planned PlayStation version of the game was cancelled.
Earthworm Jim 3D borrows much of its gameplay from other platformers of the era, notably Banjo-Kazooie and Super Mario 64. New locations in Jim's brain are opened up by collecting Golden Udders, and new levels in each location are opened by collecting Jim's marbles. Like previous Earthworm Jim games, despite many platforming elements, Jim's primary method of combat comes from shooting his Blaster.
Earthworm Jim is hit by a flying cow that sends him into a coma. Jim awakens within his own mind and discovers he has gone insane. His past villains have entered his mind and if something doesn't happen soon, Jim will be in the coma forever. His super ego has been unleashed within his mind to stop the madness. To restore his sanity he must find the golden udders of lucidity.
Earthworm Jim - The hero of the game. After getting hit by a falling cow, Jim's worst fears and anxieties were unleashed and are destroying his psyche. As a last line of defense, Jim's four worm brains embody Jim as his own superego, and send him out to collect his marbles to repair his damaged IQ. When he starts off the game, he's as smart as pond scum. More levels within Jim's brains open as Jim gets smarter.
Peter Puppy - Earthworm Jim's friend. He basically tells Jim inside of his mind what happened after the cow fell on him and what to do about the resulting turmoil his mind is in.
Snott - A booger who is also Jim's friend. He appears from time to time, giving Jim hints and telling him how to perform moves.
The Sacred Cow of Contemplation - A cow that controls the portals to Jim's brains. His powers can only be recharged when Jim finds Golden Udders. He is a master of disguise (i.e., he wears an afro in Fear, a chef hat in Happiness, a cowboy hat in Fantasy and an army hat in Memory).
When Jim enters his mind, he finds out that his four mind chambers have been taken over by his worst fears. He must collect Golden Udders to unlock the other three chambers and Green Marbles to unlock the levels within the chamber.
During its drawn-out three year development cycle, Earthworm Jim 3D changed publishers several times. This caused some problems as the game was based on the Earthworm Jim TV series which by the time of release, had been off the air for over 3 years. Also many locations displayed in early versions of the game are nowhere to be found in the released copy (such as a level set in a house, where Jim is ant-sized), and locations that were kept from early screenshots changed drastically before release. In some cases, entire characters were changed - originally, Evil the Cat was to be the boss of Fear, but was changed to Professor Monkey-For-A-Head at the last moment, although his face can be seen on the records and record needles in the level "Boogie Nights of the Living Dead". Additionally, Evil Jim, Earthworm Jim's evil twin from the TV series, was reportedly a part of the game. Early screenshots also display Jim riding his Pocket Rocket.
The characters of Earthworm Jim had to be redesigned for the shift to 3D. When the game was almost three quarters done, it suffered from framerate problems and poor animation."
Source: Wikipedia, "Earthworm_Jim_3D," available under the CC-BY-SA License.