SpongeBob SquarePants (1999)

S4E10 Enemy In-Law

Mr. Krabs' mother has found a new love, and it looks like it might be getting serious. Although Krabs wants to support her, he's utterly shocked to discover that her new boyfriend is none other than his nemesis, Plankton! Believing this is just another scheme to steal the Krabby Patty secret formula, Krabs becomes determined to expose Plankton's true intentions and put an end to this misguided romance.