Here we go, a pretty complete list of all the references (to specific episodes and general trends) in last week's South Park, which I finally got around to watching tonight. I don't recall seeing this list before, but I'm sorry if it was. (Even if someone posted something to that effect, I might have extra stuff.)
In order of what happened in the episode: -Butters wants to create a sunblocker, and General Disarray reminds him it was Mr. Burns doing that (2F16: Who Shot Mr. Burns (Part One)), and Butters decides not to do it -Cartman dreams of living under the sea with the sea people, and sings a little song - possible reference to 2F06: Homer: Bad Man -Another possible reference: When the sea people are a disappointment, Cartman flips out and insults everyone (compare Ned in 4F07: Hurricane Neddy) -The "sea people in coffee" prank bears a slight resemblance to either 9F17 or 2F32, but not a great one -Butters' next prank, which he does: Using a hack saw to remove the head of a statue in the center of town (7G07: The Telltale Head), except everyone likes it because it's a reminder of the Simpsons -His next proposal: conning the South Park residents into making a monorail (9F10: Marge vs. the Monorail), but General Disarray says it happened in episode "204" - I think they threw this in to see who was paying attention, since they knew other p-codes - the possible Simpsons 204s are: Season 2, episode 4 (7F01: Two Cars in Every Garage and Three Eyes on Every Fish) The 4th episode produced for season 2 (7F04: Treehouse of Horror) 2F04: Bart's Girlfriend the 204th episode to air: 5F20: Lard of the Dance, or the 204th episode to start production (by my calculations, that might be 5F21: The Wizard of Evergreen Terrace) - obviously none of these are 9F10, but I thought it would be interesting to see. -The next plan: a website spreading rumors about people in South Park (CABF02: The Computer Wore Menace Shoes) -Next plan: bury a skeleton with wings (5F05: Lisa the Skeptic) -(Before he flips to his next plan, a page can be seen, which looks like the previous one.) Bring the World Cup to South Park and have a soccer riot (the plot is a little bit of a stretch, but it's definitely a reference to 5F01: The Cartridge Family) -Put all the beer cans in South Park into a mixer to shake them up (compare the paint mixer for _one_ beer can), which General Disarray points out came from 9F17, "So It's Come to This" (he says 9F17 but not the whole title) -After General Disarray points out that his plans all come from The Simpsons, Butters ponders running away and joining the circus. This doesn't seem to correlate to any particular episode (General Disarray says they did that too), but three come close: 7F07: Bart vs. Thanksgiving (Bart runs away), 5F08: Bart Carny (he and Homer work at a carnival), and 8F17: Dog of Death (Homer suggests that they become a family of traveling acrobats to avoid giving up beer) -When they accidentally mix the sea people and "sea men" (think along the lines of King Homer), a tiny underwater civilation develops. See below. -When Butters comes up with a plan to replace the cherries in chocolate covered cherries with mayonnaise, he says that he watched "all 132" episodes of the Simpsons (he must have stopped at 3F02: Bart Sells His Soul) and it wasn't done. General Disarray says that they would probably be more clever, but then an ad comes on announcing that as the plot of a new Simpsons episode (would that be ZABF31: "You've Got Mayo!"?) -Soon, General Disarray looks like Bart to Butters (for him and other characters, it's a weird-looking Simpsons/South Park hybrid drawing style, with overbites and season 2 teeth, but with a definitively South Park flatness), and says "Don't have a cow, man" -Other things change in South Park as well: Tom's Rhinoplasty becomes a Wink-E-Mart (why wink?), and cooling towers and the First Church of Springfield appear in the background. A bus pulls up, and Butters encounters an Otto/Miss Crabtree combo (with her voice). Chef and Mr. Garrison come up to him, similarly drawn. When he runs away, a store can be seen on the side of the screen with a partial name: "and Sports Card Shop," clearly a reference to CBG's store. -This one's a stretch: Cartman gets more "sea men" from a guy in an alley named Ralph. I think you can figure out why, and it doesn't sound like they'd compare that to Ralph Wiggum, but they did use the name Ralph (which, as far as I know, isn't a recurring South Park character) -Cartman discovers that his sea people are advancing quickly in civilation, and notices a statue erected of him, signifying that he is a god to them (see below) -Things get more Simpsonic to Butters: he sits in a mockup of their TV room (complete with crooked boat picture), watching an announcer with a South Park voice but a Kent Brockman face tell the news about their teacher (the TV also resembles the Simpsons' model) -After Stan and Kyle come in (drawn like the Simpsons), Cartman arrives and issues a Nelson "ha-ha!" (I also noticed that the buildings in South Park were drawn so you could see their sides, which seems to be a South Park first) -Just for the sake of a list within a list, when Cartman shows everyone his sea people, the following people are shown in the Simpsons drawing style: Tweek, Timmy, Chef, Mr. Garrison, Mr. Hat, Mrs. Cartman, Stan, Kyle, Eric, and General Disarray -Cartman hopes that the sea people will build a machine to shrink him forever to be among his people, and Butters laughs, saying that they did that in 4F02 (he says that), "Treehouse of Horror" (he didn't say VII), The Genesis Tub, and gives the general plot -The gang says that after 13 years (which is correct, of course, not counting the Ullman shorts) every idea they've done has been from somewhere else: Chef points out that The Genesis Tub is a reference to a Twilight Zone episode. Butters realizes it's ok to rip off an idea, and everything appears normal to him again. On a side note, a separate faction of sea people built an idol of Tweek, and the two sides annihilate each other in a very quick mini-war. Oh well.
So there you have it. I really enjoyed that episode, and though they didn't appear to give any special thanks in the credits (or do a Simpsony theme at the end), I imagine the Simpsons producers did as well.