Veronica Mars is an American television series created by Rob Thomas. The series premiered on September 22, 2004, during network UPN's last two years, and ended on May 22, 2007, after a season on UPN's successor network, The CW. Balancing murder mystery, high-school, and college drama, the series features social commentary with sarcasm and off-beat humor in a style often compared to film noir. Set in the fictional town of Neptune, the series stars Kristen Bell as the title character, a student who progresses from high school to college during the series while moonlighting as a private investigator under the wing of her detective father.

The first season had seven regular characters. However, Thomas decided to introduce and eliminate several characters in order to create an "equally fascinating mystery" for the series' second season. Thomas needed "new blood" since he felt unable to bring back the Kanes and the Echolls and "have them all involved in a new mystery". The third season features a cast of ten actors who receive billing, an increase from the nine actors in the second. Three of the regulars in the second season are written out of the series, two new characters are introduced and two others are upgraded from recurring roles.

Kristen Bell portrays the titular Veronica Mars, a high school junior and skilled private detective. More than 500 women auditioned for the role; Bell felt that it was "just luck" that Rob Thomas saw that "I have some sass to me, and that's exactly what he wanted." Bell thought that her "cheerleader looks and outsider's attitude" set her apart from the other women who auditioned.

Teddy Dunn portrayed Duncan Kane, Veronica's ex-boyfriend and Lilly's brother. Dunn originally auditioned for Logan but ended up portraying Duncan Kane. Dunn left the series midway through the second season because Thomas felt that the Logan-Veronica-Duncan love triangle had run its course. He needed to put "other guys in her life" to keep the series fresh and attributed Dunn's removal to fan interest in the Logan-Veronica relationship, saying "It became clear that one suitor won out".

Jason Dohring played Logan Echolls, the "bad-boy 09er" son of an A-list actor. Dohring originally auditioned for the role of Duncan Kane. After his audition, the producers asked Dohring to audition for Logan's character, who was only going to be a guest role in the pilot. Dohring felt that his audition for Duncan "was a little dark", and was told by the producers that it was "not really right". The producers then asked Dohring to read for the role of Logan. Dohring acted out one scene from the pilot, bashing a car's headlights in with a tire iron. During the final auditions, Dohring read two times with Bell and met with the studio and the network. When reading with Bell, Dohring acted the whole scene as if he was the one who raped her and tried to give the character a certain evil feel.

Percy Daggs III portrayed Wallace Fennel, Veronica's best friend and frequent partner in mystery solving. Daggs auditioned for Wallace's role twice before being cast and had to go through three tests with the studio and network executives. During his first audition, Daggs read four scenes from the pilot. Just before his studio test, Daggs read with Bell and had "a great conversation". He said that she "made me feel comfortable about auditioning" and was a big reason why he became more comfortable playing Wallace as the season went on.

Francis Capra portrayed Eli "Weevil" Navarro, the leader of the PCH Biker gang and Veronica's ally. Despite often being in trouble with the law, Weevil helps Veronica solve many of her cases. He is wrongfully accused of fellow gang member Thumper's murder and is arrested at his graduation. He later becomes a janitor at Hearst College after he is cleared.

Capra reprises his role in the Veronica Mars film, in which Weevil is revealed to have since married a woman named Jade, with whom he has a daughter, Valentina.