All of SpongeHenge.
The rare Mermaid Man and Barnacle Boy trading card in The Card (seriously, how does that thing even work?)
The ending of Night Light.
Nearly all of The Inside Job.
SpongeBob's spatula going to the hospital in All That Glitters.
The perfume department in Shanghaied.
The ending of Doing Time.
Basically, nearly the entire series is weird.