"What Ever Happened to SpongeBob?" (alternatively titled "WhoBob WhatPants?" and "SpongeBob's WhoBob WhatPants?") is the 18th episode of the fifth season of the American animated television series SpongeBob SquarePants, and the 98th episode overall. It first aired on Nickelodeon in the United States on October 13, 2008.

In the episode, SpongeBob thinks that his friends don't like him anymore after he made them angry because of a few accidents and decides to leave Bikini Bottom. Along the way, he accidentally bumps his head and loses his memory. SpongeBob wanders away into a new place called New Kelp City and attempts to get a new job, unaware he is becoming a target for a criminal gang known as the Bubble Poppin' Boys, while Patrick, Sandy and a reluctant Squidward try to find him.

The episode was written by Casey Alexander, Zeus Cervas, and Steven Banks, and the animation was directed by supervising director Alan Smart and Tom Yasumi. The episode features a guest appearance by Ray Liotta as the voice of the leader of the Bubble Poppin' Boys. The episode's premiere pulled an average of 7.7 million viewers, but received mixed to negative reviews from critics.