Plopper the Pig (also known as Spider-Pig, or Harry Plopper) is Homer Simpson's pet pig from The Simpsons Movie.
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 Plopper, 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. Marge told Homer to dispose of the waste properly.
Homer was about to dispose of the waste properly, when he got a cellphone call from Lenny that Lard Donuts was having a free sale. Extremely rushed, Homer, hastily 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 and trying to kill homer. Later while the Simpson family was escaping from their house during the mob by walking across a wood board leading to the Flanders' house, Plopper pushed the board making the Simpsons fall from it (apparently trying to escape with them). He fulfilled part of Grampa Simpson's prophetic vision because of his twisted tail. Despite still being in the house when it collapsed due to the sinkhole, he survived. He was seen being placed as a present from one of Cletus's relatives at Bart and Mary's wedding.
Plopper eventually became so famous, he was put on the Springfield Wall of Fame.
Although he legally belongs to Homer, he also has been used by other members of Springfield, including Luigi by working as a truffle finder, although his job met a premature end when Lisa managed to find another way to detect Truffles, relegating him to juggling steak knives (although the way he showed the knife initially made it seem as though he was actually going to kill Plopper due to outliving his usefulness).
He returned in the season 27 episode, "Puffless".