Ray inherits a joke shop from his late uncle. Armed with a big supply of practical jokes, Ray quickly becomes a pest to his fellow Ghostbusters. But unknown to Ray, two Imps that thrive on pranks were released when he took possession of the store.
A Werechicken strikes an unsuspecting farmhouse, leaving a trail of mayhem and one very large egg. After Slimer cooks the egg and hatches it, the newborn Werechicken bites Egon, turning him into a half-man, half-chicken creature.
Peter' latest creation, a Ghost Attractor lures ghosts to the Firehouse like a magnet. He believes that it will not only save a lot of legwork, but that it will also make them millionaires. He was wrong, of course.
Janine falls in love with a rich industrialist who uses her friendship to gain access to the Ghostbusters' files, from which he creates the Robo-Buster X-1. The manufacturer claims that the Robo-Buster doesn't merely contain spirits it actually destroys them.
The Ghostmaster General is fed up with the Ghostbusters' constant interference. So he sends three ghostly bounty hunters to eliminate the heroes at the Firehouse. In the ensuing battle, the Ghostbusters are reduced to six inches in height.
A pit of toxic liquid waste has an evil effect on a long dormant Indian earth spirit. When polluted, the once benign spirit rises from its sacred resting grounds and takes possession of Ecto-1, causing the hearse to come alive.