Lord Poltergeist is a pirate ghost that appeared only in the episode "Ghoul Fools," voiced by Chris Elliott.
Lord Poltergeist runs the haunted house boat that broke down in Bikini Bottom. When SpongeBob and Patrick enter his house, Patrick thinks that he is not a real ghost, but rather a robot. They do find out he is real when he makes a pizza with Anchovies on it.
Then, Lord Poltergeist sends them out to get a new head gasket for his ship, claiming that he will keep their souls if they fail. He gets the help of Squidward, Mr. Krabs, and Sandy to give Poltergeist the gasket (but Mr. Krabs wanted to go there only for the ghost's treasure). However, once he got the head gasket, it is revealed that Poltergeist doesn't really have their souls. They were actually old orange sodas that were left out in the sun too long. He has lots of sacks of gold doubloons, and Mr. Krabs, Patrick, and Squidward try to steal away from him. SpongeBob did not like that.
When Lord Poltergeist saw Mr. Krabs, Squidward, and Patrick trying to steal his money he said "stop right there." But they ignore him by running away, although he catches them in his "void", where they are forced to suffer eternal torment. Krabs' torment was an outhouse that cost one doubloon to use, Patrick's torment was being unable to eat a donut on his head (which turns out to be worse for the donut), and Squidward's torment, obviously, was SpongeBob.
Sandy uses her ghost catching equipment to bring everyone out of the void. Soon, SpongeBob finds out that Lord Poltergeist's gold that Mr. Krabs wanted actually belonged to the Flying Dutchman. When the Dutchman found Poltergeist, he claims that he was searching the seas for the Dutchman to give him his treasure back. But this was a diversion for Poltergeist and the others to escape in the haunted house boat. However, the engine room broke down and the boat crashed.
The Dutchman then turns himself into a giant bomb and blows everyone into the void. At the end of the episode, Poltergeist was seen greeting customers in the Krusty Krab, which was somehow brought into the void (either it was possibly caught in the Dutchman's explosion too, or it was a different version that was already in the void).
As a ghost, Lord Poltergeist is very powerful. He can fly, walk through solid objects, grow and shrink at will, and possess superhuman strength.
He also possess far greater powers, able to make objects move with his mind, able to warp reality and create objects out of thin air, and banish others to a void where the worst nightmares come true. Despite his great powers, he is significantly weaker than The Flying Dutchman, and was thus terrified of his former captain.
Lord Poltergeist has a blue glow around him, while sporting a tattered naval hat and matching coat. He has a brown beard and staring green eyes.
While some say the voice of Lord Poltergeist is Tim Curry, the actual voice of Lord Poltergeist turned out to be Chris Elliott, who is known for voicing Dogbert in the animation series "Dilbert".