Sleepwalking Potion  is purple liquid that when breathed in, casts a spell that makes a human sleepwalk forever... with one known exception.
Zugg used up a canister of Sleepwalking Potion on the Ghostbusters instead of on Slimer, thinking it was a Sleeping Potion. While the Ghostbusters walked around until Goolem and Zugg tied them up. No amount of noise was able to counteract the spell. However, the Ghostbusters woke up once Slimer tried to open the refrigerator door.