The characters in the American animated television series Tiny Toon Adventures and its reboot Tiny Toons Looniversity were created by animator Tom Ruegger. The series chronicles the adventures of Buster Bunny, Babs Bunny and their various friends in the fictional city of Acme Acres. Most of the characters are anthropomorphic animals and humans based on the Looney Tunes characters.

Tiny Toon Adventures features the voices of Charlie Adler, John Kassir, Tress MacNeille, Joe Alaskey, Don Messick, Kath Soucie, Gail Matthius, Maurice LaMarche, Danny Cooksey, Cree Summer, Candi Milo, Rob Paulsen and Frank Welker, while Tiny Toons Looniversity also features the voices of Eric Bauza, Ashleigh Crystal Hairston, David Errigo Jr. and Marieve Herington. Most one-off and background characters in each series are voiced by Jim Cummings, Greg Burson, Noel Blanc, Stan Freberg. In addition to the series' regular cast, various celebrities from a wide range of professions have voiced guest characters and recurring roles.

Main characters Buster Bunny

Buster Bunny (voiced by Charlie Adler in 1990–1992 of the original series and the cancelled 2002 video game, John Kassir in 1992–1999 of the original series, Eric Bauza in Tiny Toons Looniversity) is the leading main character of the show. Buster is a young blue-and-white male bunny rabbit with a red shirt (red hoodie in the reboot) and white gloves, and is Babs' best friend. In the last episode, It's a Wonderful Tiny Toon Christmas Special, Babs states that Buster is her boyfriend. Bugs Bunny is Buster's mentor. Adler voiced Buster in the cancelled video game Tiny Toon Adventures: Defenders of the Universe. Buster is based on the Chuck Jones version of Bugs Bunny.

In the Looniversity reboot, Buster is Babs' twin brother. Given the many different aspects of their personality traits, "Adventures" Buster and "Looniversity" Buster are practically two different characters. In "Extra, So Extra", his middle name is "Filmore."

Babs Bunny

Barbara Anne "Babs" Bunny (voiced by Tress MacNeille in 1990–2002 of the original series, Ashleigh Crystal Hairston in Tiny Toons Looniversity) is a main character of the show. Babs likes doing impressions and wearing disguises and dislikes being addressed by her full name. She is a young pink female bunny rabbit with a yellow shirt, purple jacket in the reboot, violet skirt, and violet bows on her ears. Babs is based on the Bob Clampett version of Bugs Bunny.

In Looniversity, a different version of Babs is "Looniversity" Buster's twin sister. It also shows an episode of Babs and Lola together for the first time with the adult female rabbit being her mentor.

Plucky Duck Plucky Duck (voiced by Joe Alaskey in 1990–2013 of the original series, Nathan Ruegger as "Little Plucky" in 1991–1994 of the original series, and David Errigo Jr. in Tiny Toons Looniversity) is a young green male duck in a white tank top. Plucky is based on Chuck Jones' Daffy Duck. Plucky is friends with Babs Bunny, Hamton J. Pig and Buster Bunny, despite the fact that they frequently annoy each other. Plucky is quite jealous of Buster and Babs's popularity, similar to Daffy's insane jealousy of Bugs's popularity, and very often tries to undermine it in various sneaky, underhanded ways. That said, Plucky is many times shown to be caring and genuinely heroic. Plucky constantly pines for the love of Shirley the Loon, though she has very little patience for him even though she favors him out of any other men.

In Looniversity, Plucky's real name is revealed to be Pluciferous von Mallard Duck and he wears a black shirt instead of white tank tops. In the series, he seems to have come from a more wealthy background due to having a more snobbish attitude with a less antagonistic and vastly more egotistic behavior and takes cartoon acting more seriously. He also loves competing with Buster. In the episode "Spring Beak", his parents are revealed to be world travelers named Ralph and Maria and he always calls them by their first names rather than mom and dad.

Hamton J. Pig

Hamton J. Pig (voiced by Don Messick in 1990–1995 of the original series, Billy West in 1997–2002, David Errigo Jr. in Tiny Toons LooniversityHamton J. Pig at Don Markstein's Toonopedia. from the original on December 2, 2015.) is a young pink male pig who wears blue overalls. Based on Porky Pig, Hamton's role in the series is as a straight man, often against Plucky Duck's antics. The only difference is that unlike his mentor Porky, Hamton never stutters. Hamton is an overeater who is obsessed with cleanliness. In one episode, it is revealed that he is interested in Fifi La Fume. Billy West took over the role of Hamton in a few video games after Don Messick's death, including 1999's Tiny Toon Adventures: Toonenstein.

In Looniversity, Hamton wants to be a doctor while doing performances and suffers from indecisiveness. His mother was changed to Joan, who attended ACME Looniversity which led to becoming a famous performer and hopes her son follows her footsteps. He is also given a stutter just like Porky, as well as a Southern accent.

Fifi La Fume Fifi La Fume (voiced by Kath Soucie in 1990–2002 of the original series, Marieve Herington in Tiny Toons Looniversity) is a young, purple and white female skunk with a pink bow in her hair. Based on Pepé Le Pew, she shares his character traits of having a French accent and aggressively seeking romance, only to find the object of her affection is repulsed by her odor and aggressive advances. Unlike Pepé Le Pew, Fifi feels more hurt by rejection and even bursts into tears about it. Fifi often unsuccessfully attempts to chase males who have ended up with white stripes painted down their backs, such as Furrball, Calamity Coyote, and Little Beeper. Fifi does not mind if males chase her and can control her stench, although it sometimes can be triggered when she becomes romantically in love. Some episodes downplay her romantic life, and show her doing random group activities with other characters. She lives in a striped 1959 Cadillac in a wrecking yard. Hamton is one of the few boys who genuinely love her back, and he has attended the Looniversity prom with her.

In Looniversity, she wears a black sweater, is French-Canadian, and is less focused on romance.

Shirley McLoon Shirley "The Loon" McLoon (voiced by Gail Matthius in 1990–2002 of the original series, Natalie Palamides in Tiny Toons Looniversity) is a young loon citizen of Acme Acres. She is based on Daffy Duck's main love interest, Melissa Duck. She speaks with a thick Valley girl accent. Although she seems reasonably intelligent, she is obsessed with superficial New Age paraphernalia. Her name is a pun on fellow New Age aficionado Shirley MacLaine, and she later appeared in an episode of Animaniacs, standing next to MacLaine. She can tell fortunes, obtains psychokinetic powers, and is a skilled ballerina; the former hobbies earning her the derisive nickname "Shirley the Loon". She appears not to notice the negative connotations of the nickname and often recites "Oh, what a loon I am" while meditating. Shirley is romantically pursued by Plucky Duck and Fowlmouth, although she seems to tolerate Plucky's self-centeredness more than Fowlmouth's publicly embarrassing crude behavior and bad language. Despite her annoyance with Plucky's flirtatious gestures, Shirley does seem to care for him and occasionally dates him. Shirley often hangs out with Babs and Fifi.

In Looniversity, Shirley serves as the RA for Merry Melodies hall while also being a student, with her new design includes her hairstyle, wearing glasses, has earrings on her sides and she wears a skirt that covers her bottom instead of it being exposed. She has a different accent and no longer uses the words like or junk in her sentences.

Montana Max Montana Max (voiced by Danny Cooksey in 1990–2002 of the original series, Candi Milo in Tiny Toons Looniversity), nicknamed "Monty", is a young brown-haired boy and the main antagonist. He is an evil, loud-mouthed, and money-hungry tycoon. Monty has an American location in his name and is often an enemy to Buster Bunny, much like Yosemite Sam is to Bugs Bunny; similarly, the character may reference the addition of Sam to Bugs Bunny shorts to create a threatening antagonist, as the pilot episode compares him to the other "pushover" villains. Like Elmyra, Monty is a human and attends Acme Looniversity. He is portrayed as a very wealthy and stubborn boy who lives in a mansion and does not have any siblings or friends. However, he does have a (rarely shown) sweet side like finding out where meat comes from in "Slaughterhouse Jive" and has been shown to have a good imagination with help from the personification of his imagination as seen in "Fit to Be Toyed". Some episodes that he stars in features his parents whose heads are never seen and are shown to keep him in line. Elmyra likes Monty a lot, though he usually feels nothing but annoyance towards her. Max once had to tolerate Elmyra in "My Dinner with Elmyra" because his parents have become friends with Elmyra's parents according to his mother, but after Elmyra kissed him at the end of the date, he said to himself in private that he thought he was in love.

In Looniversity, Montana Max has the personality of a con artist.

Recurring characters Elmyra Duff Elmyra Duff (voiced by Cree Summer in both showsElmyra Duff at Don Markstein's Toonopedia. from the original on June 17, 2016.) is a redheaded young girl who wears a blue blouse, white skirt, black Mary Janes over white socks, and a blue bow with a skull at the center. Her design and name are a play on Elmer Fudd; much like her surname, she is also a reversal, having a crushing affection for animals that makes her unintentionally dangerous initially falling into the stereotype of the "spoiled and piercing-voiced girl." She is one of the few human characters in the series and she attends Acme Looniversity with the animal characters, where she also serves as the nurse. In two episodes, Elmyra's family is shown including her mother, inventor father, typical '90s teen sister, younger brother, super-strong baby brother, and a maid.

Elmyra was also featured as a co-protagonist and ally to Pinky and the Brain in the spin-off Pinky, Elmyra & the Brain. Though initially claimed by Cree Summer to be removed from the show, Elmyra appears in Tiny Toons Looniversity as a photographer obsessed with taking pictures of animals. She also appeared in Animaniacs, in the episode segment “Lookit The Fuzzy Heads”, attending a group therapy session with Yakko, Wakko, and Dot Warner. Furrball