Animated television characters introduced in 1991

Angelica Pickles is a cartoon character who appears in the Nickelodeon shows Rugrats, All Grown Up!, and Rugrats Pre-School Daze, and is among one of the series' original characters. She is a spoiled brat and the cousin of Tommy and Dil Pickles, and serves as the main antagonist of the series, but she's portrayed as an anti-heroine in the films who would side with the babies near the end against the respective main villains. In 2002 TV Guide ranked Angelica Pickles 7th in their list of "Top 50 Greatest Cartoon Characters of All Time".

Snake Jailbird (usually referred to as simply Snake) is a recurring fictional character in the animated television series The Simpsons, who is voiced by Hank Azaria. Snake's first appearance was in the episode "The War of the Simpsons". His catchphrase is "Bye!", which he usually says when he's in trouble. His real name is Albert Knickerbocker Aloysius Snake, although a Simpsons card says his name is Chester Turley. He was named the 19th (out of 25) of IGN's Top 25 Simpsons Peripheral Characters.

Dr. Nicholas Riviera (usually referred to as simply Dr. Nick) is a recurring fictional character in the American animated sitcom The Simpsons. He is voiced by Hank Azaria and first appeared in the episode "Bart Gets Hit by a Car". Dr. Nick is an inept quack physician, and a satire of incompetent medical professionals. Upon entering a scene, Dr. Nick's catchphrase is "Hi, everybody!", with the characters present immediately responding (often in chorus) "Hi, Dr. Nick!".

Professor John I.Q. Nerdelbaum Frink Jr., or simply Professor Frink, is a recurring character in the animated television series The Simpsons. He is voiced by Hank Azaria, and first appeared in the 1991 episode "Old Money". Frink is Springfield's nerdy scientist and professor and is extremely intelligent, though somewhat mad and socially inept. Frink often tries to use his bizarre inventions to aid the town in its crises but they usually only make things worse. His manner of speech, including the impulsive shouting of nonsensical words, has become his trademark.

William "Willie" MacDougal, more commonly known as Groundskeeper Willie, is a recurring character on The Simpsons, voiced by Dan Castellaneta. He is head groundskeeper at Springfield Elementary School. Willie is almost feral in nature and is immensely proud of his native Scotland. He is easily identifiable by his flaming red hair and beard, as well as his aggressive temperament and strong Scottish accent.

Lionel Hutz is a fictional character in the American animated TV sitcom The Simpsons. He was voiced by Phil Hartman, and his first appearance was in the season two episode "Bart Gets Hit by a Car". Hutz is a stereotypical ambulance chasing lawyer in Springfield with questionable competence and ethics. He is nevertheless (or thus) often hired by the Simpsons. Following Hartman's murder in 1998, Hutz was retired out of respect; and his final speaking role was in the season nine episode "Realty Bites" five months earlier.

Comic Book Guy is the common, popular name for Jeffrey "Jeff" Albertson, a recurring fictional character in the animated television series The Simpsons. He is voiced by Hank Azaria and first appeared in the second-season episode "Three Men and a Comic Book", which originally aired on May 9, 1991. Comic Book Guy is the proprietor of a comic book store, The Android's Dungeon & Baseball Card Shop. He is based on "every comic book store guy in America" and represents a stereotypical middle-aged comic-book collector. He is well known for his distinctive accent, disagreeable personality and his catchphrase, "Worst [blank] ever!"

Reptar is a fictional character from the American animated television series Rugrats. It is a green mutated Tyrannosaurus (and sometimes appears in red-violet and lilac) with rounded, blue spike-like appendages on its back, which intentionally causes it to resemble and spoof Godzilla. Outside of Rugrats-related films, Reptar appears as a playable character in the Nickelodeon Kart Racers and Nickelodeon All-Star Brawl video game series.

Mona Penelope Simpson (née Olsen) is a fictional guest character in the animated television series The Simpsons. She has been voiced by several actresses, including Maggie Roswell, Tress MacNeille, Pamela Hayden, and most prominently, Glenn Close. Close's performances as Mona have been well received by critics and she was named one of the top 25 guest stars on the show by IGN.

Troy McClure is a fictional character in the American animated series The Simpsons. He was originally voiced by Phil Hartman and first appeared in the second season episode "Homer vs. Lisa and the 8th Commandment". McClure is a washed-up actor who is usually shown doing low-level work, most notably hosting manipulative infomercials and questionable educational films. He appears as the main character in "A Fish Called Selma", in which he marries Selma Bouvier to aid his failing career and quash rumors about his personal life. McClure also hosts "The Simpsons 138th Episode Spectacular" and "The Simpsons Spin-Off Showcase".