Pigs are a common creature in the Invader Zim universe, appearing several times (Jhonen Vasquez has stated that he "likes the word"). Most pigs are shown as piggy toys, posters, and the like. In other words, most appear as inanimate objects, though a few have made appearances as live ones. Bloaty is a major example, and Pigboy made his debut in "The Frycook What Came from All that Space". In "Game Slave 2", flaming vampire pigs are the main foes of the game "Vampire Piggy Hunter" for the Game Slave console.
Also, in "Bad, Bad Rubber Piggy", it was shown that GIR has a vast amount of rubber piggy toys. There was also a pork/pig head in the Carne stand in "Walk Of Doom". In the 2008 game Nicktoons: Android Invasion, GIR leaves pigs in each of the underground worlds of Bikini Bottom, Miracle City, Amity Park, Retroville, and Dimmsdale.
Pig has been seen as GIR's friend in many episodes. One of them was in "Germs", where GIR took the pig to his "room"; later in the episode, GIR was seen bidding farewell to Pig at the entryway of the base (the noises in the background suggested that Pig had a motorcycle). In "Battle of the Planets", GIR was seen again having a tea party with Pig. GIR's porcine companion also made a cameo in "Gaz, Taster of Pork", as GIR's plus-one for Pig Girl: The Movie.
A light-up pig was seen in the episode "Megadoomer" very briefly before GIR disconnected it to plug in the Megadoomer.
Rubber PiggyThe Rubber Piggy is a toy that GIR plays with, making its first appearance is in "Bad, Bad Rubber Piggy" as a part of Zim's diabolical plan to ruin Dib's life. GIR was later seen playing with it and other ones in "Planet Jackers" and "Battle of the Planets".
Shadowhog appeared only in the episode "Gaz, Taster of Pork", in which he gives Gaz the "gift" of having everything she ate to taste like pork. After she travels to his realm and passes his trials, he returns her to normal.