Ghash (also known as Mr. Ugly) is a massive poltergeist who wears a ghostly trench coat accompanied by a top hat.
After three nights in a row, coincidentally culminating on Winston Zeddemore's birthday, the Ghostbusters encountered Ghash, leader of a group of poltergeists. By feeding on the lesser entities, Ghash was able to increases his P.K.E. and gain the ability to roam. Due to a mishap at Winston's party, Slimer left the Firehouse and followed several entities to Ghash. He soon absorbed all of these entities to become unstoppable. The Ghostbusters adjusted their equipment to focus primarily on Slimer's unique frequency of 500,000 Mega Hertz and extract him from Ghash. They were then able to trap him and place him in the Containment Unit.
Ghash's demeanor appears to be an odd combination of qualities, such as Dracula, The Grim Reaper, and a wheat harvester.
When large groups of ghosts band together for threatening haunts and chaos, there is always one that stands out and leads the pack. Ghash had the proper personality and appearance for this specific role. Even though he was an evil being that cared for nothing more than immense power, he gave lost ghosts like Slimer a false sense of security and a feeling of being wanted.
Spectral Absorption: Ghash's signature trait was the ability to absorb other spectral entities by consuming them though a massive mouth in the middle of his torso. The more entities Ghash absorbed, the bigger and stronger he became. Once a ghost was inside Ghash, they would weaken as their powers were drained until there was nothing left.
After he consumed the other members of his "Ghost Gang", he could:
Lasers: Ghash demonstrated his powers by shooting beams from his eyes.
Superhuman Strength: He was able to crush through the roof as he got larger.
Telekinesis : He used his telekinetic abilities to control floorboards and disarming the Ghostbusters by removing their Proton Packs and tossing them to the other side of the room.
Ghash also became a Roamer, he was no longer fixed to one location as a standard poltergeist is.
The name Ghash comes from the Storyboards and Script files for the episode "Slimer, Come Home" provided in Volume One, Disc Five of The Real Ghostbusters Dvd Box Set.
- "Slimer, Come Home"
- Ghash was the main enemy. Throughout the episode, he showed the members of his Ghost Gang how to properly scare people, and gave Slimer a place when he left the Firehouse.
- "Xmas Marks the Spot"
- "Sticky Business"
- As a cameo in the Containment Unit. He attempted to absorb Slimer while he was looking for the Stay Puft Marshmallow Man.
- Opening credits and the outro,  but was not featured in any episodes.
- Like Samhain, Ghash had an altered appearance (even though he retained his original appearance in the end credits). His coat was made red and so was his top hat. He was also changed from pale to yellow and had different teeth and a brown nose. It is likely that Ghash wasn't featured in any episodes because he was a more minor adversary of the Ghostbusters.