
Trivia: In "Where's Gary?" when Spongebob takes the Dirty Bubble Challenge, look closely at the paddleball box; it has the Nickelodeon logo on it.

Revealing mistake: In "Patrick! The Game," when Squidward holds out the notepad, it's obviously written on. Just when the bubble transition comes, the notepad and all the other papers on the floor clear themselves.
Answer: I believe this is the Season 6 episode "Spongicus".