The Season 9 episode, "Plankton's Pet", even showed SpongeBob voluntarily helping out Plankton by not just selecting a pet for adoption, but also searching for it after it goes missing.

When SpongeBob's parents go missing, he suspects that his cousin BlackJack, the family bully who used to torment him when they were little, has kidnapped them. While brushing his teeth ...

The Bikini Bottomites go crazy and they all believe that Spongebob and Plankton stole the secret formula. The two new teammates create a time machine to get the secret formula before it disappears ...