Enemy In-Law/Mermaidman and Barnacleboy VI: The Motion Picture - S4-E7
Other mistake: Plankton's phone doesn't have a 0 button on it.
Casual Person
29th May 2013
SpongeBob SquarePants (1999)
29th Jan 2013
SpongeBob SquarePants (1999)
You Don't Know Sponge/Hide and Then What Happens - S8-E3
Other mistake: It is revealed in this episode that Patrick is right-handed. However, in the season 4 episode Krusty Towers, when asked to sign the Krusty Towers guest register, he is shown doing so with his left hand.