Mrs. Pop (The Huff)

Mrs. Pop is an insane, evil alter-ego of Mrs. Puff whose main goal is to kill SpongeBob. She also has another (more deranged) alter-ego named The Huff, a monster truck driver.

Origin
In the real episode, Demolition Doofus, Mrs. Puff got badly injured from one of SpongeBob's driving tests and caused her inflation sac to deflate. No longer able to Puff, her hatred towards SpongeBob reached a new dangerously high level. The name Mrs. Pop was coined by SpongeBob.

Later, she got an idea to enter SpongeBob in a demolition derby in hopes of getting rid of him. But it didn't work. She soon turned psychotic and became The Huff, then tried to run him over with a giant monster truck. Doing so, she regained her Puffing ability and reverted to her normal self, but destroying her boating school in the process.



Fanon
In fanon episodes, Mrs. Pop/the Huff could return. Either Mrs. Puff will lose her Puffing ability again, or the alter-ego could somehow become a separate character. It is also rumored she may be more psychotic than in the actual show.