Plankton walks to the Chum Bucket stinking with the stench of "Failure" as he calls it, and Karen is in a very happy mood. Karen then smells Plankton and gives him a bath, taking off his skin, which is revealed to be his clothes. After he's washed, Plankton learns that it was his and Karen's wedding anniversary and that Karen got him a copy of the Krabby Patty secret formula for his present, but he can't have it until he gets her a present.
Plankton is crying on the road and SpongeBob hears the crying sound. He sniffs like a dog and soon runs into Plankton. He tells SpongeBob the news and SpongeBob yells to all of Bikini Bottom that there's a "Love Emergency." SpongeBob then tells Plankton that his present has to come from the heart, and he suggests a serenade. Plankton then remarks that he cannot sing, and SpongeBob takes him to the pineapple and works on Plankton's vocal cords. Plankton sings so high that he breaks the glass Squidward was drinking out of his juice and Sandy's helmet breaks while she was walking then she runs back to her treedome for air. Then, Plankton goes off to serenade Karen.
Plankton walks into the Chum Bucket and starts singing a mariachi-style song, and SpongeBob and Patrick play guitars in the background, wearing Mexican-style clothing and mustaches. Plankton also shakes maracas. Karen cries when it is over, and then she starts uploading the Krabby Patty secret formula. SpongeBob is mad at this, so he unplugs what he thinks is Karen, but was just the coffee maker. Karen finally uploads the formula, but she starts crying again, and she breaks down and shorts out, leaving Plankton still without the secret formula, making Plankton confused. She then shuts down, and the E.M.I.L.P (Emergency Mother-In-Law Program) uploads and starts nagging, saying that Karen could have married the ATM, someone with money.
This episode is number 13 on Tom Kenny Top 20 on iTunes. His description says:
"Kind of obscure, but one of the few episodes to focus on the 'honeymooners-like' marriage of Plankton and Karen (just a microorganism and his computer wife tryin' to get by). I love how Plankton swings between henpecked husband and world-conquering megalomaniac."
Karen has a Boston accent while her "mother" has more of a New York/Jersey accent.
Plankton's failures are usually his own fault or another character's. In this episode, it seems to be Karen's fault for crying and short circuiting. It may also briefly be Plankton's fault for forgetting their anniversary.
Karen is upset with Plankton for not having an anniversary gift for her, but in the end, she is the one who fails to give the other an anniversary gift.
SpongeBob was pressing the keys Ctrl, Alt, and Del. Karen is most likely based on a Windows system, since these keystrokes either allows the user to log on, opens a Task Manager or opens a screen with options like Task Manager on a real Windows computer.
On the Nickelodeon schedule, this episode is called "Green Anniversary."
SpongeBob knew what butterflies were in this episode, but not in "Wormy." Therefore, this episode must come after "Wormy."