Plopper

Plopper the Pig (aka Spider-Pig or Harry Plopper) is Homer's pet pig. Homer first meets Plopper the Pig when he and Bart are in Krusty Burger. Plopper is being used in a video commercial for a new Burger coming out, featuring a variety of pork. After the commercial is wrapped Krusty says to kill the pig, Homer overhears and exclaims 'You can't kill him if he's wearing people clothes' as Plopper was wearing a chefs hat. Plopper avoids his death thanks to Homer and the two become rather close, even coming close to kissing. Homer treats Plopper more like a son than Bart, which adds to Bart's disliking of Homer. It is Ploppers 'Pig Crap' and Homer's negligence which tips the pollution in Lake Springfield over the edge, causing one of worst moments in Springfield's history.

Biography
Plopper was adopted by Homer after he sees him featured in a Krusty Burger commercial filmed live at one of Springfield's Krusty Burger locations when he is about to be killed (he believes that animals wearing people's clothes shouldn't be killed). Although Marge wanted Homer to get rid of the pig because a warning seemingly crazy Abe Simpson had of "twisted tail" being one of the signs being trapped forever, Homer kept the pig. Homer then played with Spider-Pig, particularly making it seem like he is crawling on the ceiling to spoof Spider-Man and leaving pig tracks all over the place. Homer puts his droppings in a giant silo that reads "pig crap" in the back yard. He then renamed him Harry Plopper to spoof Harry Potter. Homer dropped his silo of droppings in Lake Springfield. This caused the lake's water to become mutagenic, leading to Springfield getting covered by a dome and an angry mob going after the Simpsons. He fulfilled part of Grampa Simpson's prophetic vision because of his twisted tail.

Plopper eventually became so famous, he was put on the Springfield Wall of Fame. At some point he nearly endangered the town again, although this time by somehow causing a nuclear meltdown that would happen in approximately thirty minutes. Just like Trappucino, this also resulted in most of the townsfolk forming an angry mob and trying to kill Homer (as he was technically responsible due to being Plopper's owner.). Homer eventually manages to stop the disaster before it could happen.

Behind the Scenes
The Spider-Pig song gag which parodies the Spider-Man theme is arguably the most remembered and popular scene in the movie. It was featured on many trailers for the film. According to the writing staff, it was one of the latest additions to the film.

When the Simpsons escape Springfield, Chief Wiggum shoots at the sinkhole The Simpsons escaped through and the house gets sucked in and demolished by it and it was believed that Plopper possibly died. However, the release of the DVD shows an a slightly alternate ending, where Plopper is helping out with the reconstruction of a Santa's Little Helper's doghouse, along with the Multi-eyed squirrel and SLH. In addition, he is in the couch gag in He Loves to Fly and He D'ohs- Homer cuddles him and refers to him as his "summer love". He has also made brief cameo appearances in the Heck House segment of "Treehouse of Horror XVIII," and later appears in "All About Lisa" and "Apocalypse Cow".

Spider-Pig Song
Spider Pig, Spider Pig,

Does whatever a spider-pig does.

Can he swing from a web?

No, he can't, he's a pig

''Look out! He is Spider-Pig''