Gullible Pants/Overbooked - S6-E19
Other mistake: In the episode where SpongeBob has to do 3 things in 1 night, near the end, they all get frustrated for not doing their tasks. Look at Mr. Krabs. He runs over to SpongeBob and behind him is bubbles. Impossible, because in Sandy's dome is air.
Other mistake: In the English dub of the series, Tai's last name is Kamiya; however, when he makes reference to the family name plate his father put on the front door in this episode, the name displayed is Yagami. (00:03:00)