The Hamster appears as a helpful animal companion in the level Down the Tubes of the original video game. If Earthworm Jim releases the Hamster from its cage and climbs on its back, it will immediately start charging straight ahead, and Jim can ride it like a mount. It is very fast, and its massive incisors can bite through any enemy in the level, including the kitten guards and Number Four himself. However, it cannot be taken into the final "battle" with Bob the Killer Goldfish.
The Hamster also made a brief appearance in the Earthworm Jim comics, in which it fulfilled a similar role.