Taquito

Taquito is a chihuahua that Milhouse got as a pet as a reward for not wetting the bed for a week, and is one of the pets that the Van Houtens have.

He is first seen in the Season 6 episode, "Bart's Comet", when the comet disintegrated into a tiny rock, fulfilling Homer's prediction about the comet being no bigger than a chihuahua's head^[1].

In "Radioactive Man", he is accompanied with Bart when he dressed up to try and land the role of Fallout Boy in the Radioactive Man film, but he was rejected for being too short.^[2]

Nineteen episodes after he made his second appearance, he appeared in "22 Short Films About Springfield" in Bumblebee Man's house during Bumblebee Man's story^[3].

After his third appearance, Taquito didn't appear in the show again until twenty-one seasons later in the Season 28 episode, "Dogtown", as the main leader of the pack when the dogs of Springfield turn against the town upon learning they've been advocated in a trial against Gil Gunderson. While he digs into the Van Houtens' front yard flowers, Luann tells Kirk to stop him, but he reluctantly sprays on Taquito, making him angry. Kirk tells Taquito not to hurt him and that he's exposing his belly, but Taquito keeps getting angry, causing all of the dogs in Springfield to get angry as well. Later, when Bart and Lisa look for Santa's Little Helper, Taquito and the other dogs walk toward the duo in anger, and Lisa points out the alpha, which is Taquito who acts as the dogs' alpha, until Marge arrives, confronts him, and finishes him off with a kick before apologizing for kicking him. He later befriends Gil, intending to eat his corpse when he dies^[4].