Most were guest stars (Adam Scott) while a few had recurring roles (Amanda Seyfried). Some were already established stars (Jonathan Taylor Thomas) while others were destined for Marvel-level fame (Tessa Thompson).
See who popped onto the series...
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Gossip Girl star Leighton Meester was also a gossip on Veronica Mars. She appeared in two episodes as Carrie Bishop, an 09er known for spreading rumors and the student with whom Mr. Rooks was accused of sleeping. Meester was later replaced by actress Andrea Estella in the film, which focused on the mystery of who killed Carrie.
Alia Shawkat's storyline in the Season 2 episode was much heavier than Cera's. Her character, Stacy, was the victim of an on-campus serial rapist who shaved Stacy's head after assaulting her.
You can catch Oscar-nominated actress Jessica Chastain delivering an emotional performance as Sarah, Veronica's pregnant neighbor with a sad past, in a Season 1 episode.
Simple Life star Paris Hilton appeared in a Season 1 episode as Logan's snobby, cheating girlfriend, Caitlin Ford, who committed credit card fraud.
Reality TV star Kristin Cavallari made her scripted debut as Kylie Marker, a lesbian cheerleader who extorted another queer student into coming out in a Season 2 episode.
Prolific actor Ed Begley Jr. is featured in six episodes of Season 3 as Cyrus O'Dell, the dean of Hearst College whose murder Veronica was tasked with solving.
Ever the MVP of any show's guest star roster, Jane Lynch appeared in an early episode of the series as Mrs. Donaldson, the Neptune High faculty member who resists Veronica's request to have the school's election results recounted.
Kyla Pratt has plenty of credits to her name, and the list includes a Season 1 appearance as a Neptune High student who falls victim to a scam.
Hold up, Xena: Warrior Princess has been on our favorite UPN/CW series? That's right: Actress Lucy Lawless makes a guest appearance as FBI Agent Morris in a Season 2 episode of Veronica Mars.
High School Musical actress Monique Coleman has a small role in a Season 1 episode as a girl who offers guidance to Veronica on how to find her missing friend.
Do you recognize Victoria Sutherland without her fangs? The Twilight vampire is a sorority girl in a Season 3 episode of Veronica Mars.
Before he hit the big screen as Jimmy Olsen in Superman Returns, Sam Huntington could be seen as 09er Luke Haldeman in two episodes of Season 1 of the Kristen Bell-led series.
Theo Rossi played troubled teen Norris Clayton, who is framed in a bomb plot, but you probably know him for his role as Juan Carlos "Juice" Ortiz on FX's Sons of Anarchy.