The Succubus

South Park episode The Succubus a.k.a. Chef's Mama
South Park - Episode 0303 - Original Air Date: 21st April 1999.
This South Park episode was write by Trey Parker.
Chef has a new woman enter his life, and he no longer has much time to spend with the boys. He then decides to marry her and get a new job, leaving the school cafeteria to be run by other employees of South Park Elementary. The boys soon discover that the soon-to-be Mrs. Chef is actually an evil Succubus that intends to devour Chef's soul once they get married and set out to stop her.
In this South Park episode, Chef's parents have their 1st appearance and Kenny dies twice.
On the commercials promoting this episode, Ms. Crabtree was shown as the new school cafeteria chef. When the episode actually aired, the new cafeteria chef was a new character called Mr. Derp.


South Park Spoiler Alert!
(The complete plot for this South Park Episode)

Eric Cartman must go to the local eye doctor, whom he hates because the doctor always makes fun of his obesity by referring to him as "Piggy". Cartman is told that he has bad vision and has his eyes dilated; he is later given a pair of thick-rimmed glasses which are then stapled to his head so that he cannot take them off. Later, he and the other boys discover that Chef has quit his job at South Park Elementary and has been replaced by Mr. Derp, a cliché cartoon character, satirizing Pauly Shore, who tries (and fails) to win them over with his poor slapstick comedy gags.
They then find out that Chef has a new girlfriend, Veronica, played by Michael Ann Young, who has caused his life to change from that of a free-spirited, soul-singing hipster to that of a mediocre, religious paper pusher. She is also extremely fond of singing the love theme from The Poseidon Adventure, "The Morning After" at inappropriate times. The boys believe that she is trying to steal Chef away from them and are dismayed when they discover that the two are planning to get married.
Not wanting Chef to go to, the boys seek advice from Mr. Garrison, who suggests that Veronica is a succubus: a demoness sent from Hell to prey on and suck the life out of men. The boys go to warn Chef of this, but instead they meet his parents, who tell them about their frequent meetings with the Loch Ness Monster, claiming that the beast is stalking and constantly pestering them for a sum of "about tree fiddy" ($3.50). (This is a take on constant jokes mostly from black comedians, like Richard Pryor, about unusual people asking for money or food during hard times.)
Meanwhile, a botched attempt at laser eye surgery leaves Cartman temporarily blinded. Whilst the others mock him, Veronica comes to visit them. She manages to convince them that she is not a monster but, just as she is about to leave, suddenly takes on a demonic face, laughing maniacally and declaring that they cannot stop her from marrying Chef. The boys try to tell Chef of this at the rehearsal dinner, but he angrily shuts them out. They go back to Cartman's place to formulate a plan to stop the wedding.
The boys discover that a succubus controls the minds of men with a melody and that playing it backwards will vanquish it. They remember that Veronica always sings "The Morning After" and proceed to learn how to sing the song backwards. At the wedding, they play a tape of the song backwards while Stan and Kyle sing the words in reverse order. Veronica begins to lose her hold on her human form. When the tape gets jammed, she peels off her human disguise and becomes a bizarre red-eyed, bat-winged, hag-like monster, flying around and wrecking the church (killing Kenny in the process). When the boys finish singing the song, Veronica is sucked back into Hell. Chef, no longer under her evil spell, apologizes to the boys for ignoring them and eventually returns to their school as the chef and as his old self.
Cartman returns to his optometrist, who tells him that, with eyes as bad as his, he will always have to wear glasses. He solves this problem by convincing the doctor to give him an eye transplant, using Kenny's frozen head as a donor. The optometrist then asks for $3.50, suggesting that Chef's parents' tales were not entirely fabricated.