The Splinter is a small piece of wood that SpongeBob accidentally gets after he tries to pull out his spatula from the ceiling and falls.
It immediately makes him feel pain and is hard to get it out. SpongeBob tries removing it but he fails, so he contacts Patrick who puts trash from a dumpster onto it, making it swollen and turn purple with green pus. Squidward tells Mr. Krabs about the splinter as he felt it would send SpongeBob back home. At the end of the episode, Mr. Krabs pulls it out, it explodes into confetti, and then into green pus at his dismay.