Slimer! And the Real Ghostbusters

The Dirty Half-Dozen (1x18)

Air date: Oct 29, 1988

Ghoullem and Zugg, the ghost gangsters from "Scareface", return from the South Pole to get revenge on Slimer. They put the Ghostbusters to sleep with a sleep-walking potion, and Slimer is the only one who can rescue them (which is just what Ghoullem and Zugg want). However, Slimer doesn't go unprepared, as he gets all his friends to help him.