24 featured plenty of big names over its eight original seasons, but even more impressive were the guest stars. Many of the actors who only popped up for an episode or two have gone on to become much bigger stars, whether as leading ladies on network dramas or stars of the funniest shows on TV. Here’s a look back at 24 stars you might be surprised to find out were a part of one of Jack Bauer’s very long days. Also, check out the saddest deaths from eight seasons of 24.

#24 Silas Weir Mitchell

Before he was Nick’s blutbad BFF on Grimm, Mitchell was a part of the first season of 24 as Eli Stram, one of the bad guys holding Jack’s wife and daughter hostage. He was also the man who raped Teri Bauer.

Silas Weir Mitchell

#23 Misha Collins

Before he was the heroic angel Castiel on the Supernatural, Collins was Alexis Drazen in 24 season 1, the son of a Serbian military leader (played by Dennis Hopper) who worked with his brother to plot the assassination of David Palmer and the rescue of their father.

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#16 Daniel Dae Kim

Before he was Chin Ho Kelly on Hawaii Five-O or Jin Kwon on Lost, Kim played CTU field agent Tom Baker in seasons 2 and 3 of 24, helping Jack on several tactical missions. Unlike most CTU field agents not named Jack Bauer, he didn’t die.

#15 Kevin Chapman

Before he was Detective Lionel Fusco on Person of Interest, Chapman was Warden Mitchell in the prison holding Ramon Salazar at the start of 24 season 3. Interestingly, he also played a Coast Guard officer who informed Jack that his daughter wasn’t dead in the first season finale.

#14 Gina Torres

Before she was Jessica Pearson on Suits, Torres was far less stable as Julia Milliken in 24 season 3, Wayne Palmer’s ex-girlfriend who got mixed up in a conspiracy and ultimately killed Sherry Palmer.

#13 Paul Blackthorne

Before he was Quentin Lance on Arrow, Blackthorne was the villain at the end of 24 season 3, a former MI6 agent named Stephen Saunders who tried to release a deadly virus.

#12 Simon Templeman

Before he was the silly and ridiculous alien Larry Bird on The Neighbors, Templeman was an MI6 agent named Trevor Tomlinson who tried to help Jack in 24 season 3, but was then almost immediately killed by the terrorists in a helicopter attack on his office.

Simon Templeman

#11 Leighton Meester

Before she was Gossip Girl’s Queen B Blair Waldorf, Meester was Debbie Pendleton, the girlfriend of teenage terrorist Behrooz Araz in the fourth season of 24. Her penchant for sticking her nose where it didn’t belong led her to be poisoned by Behrooz’s mom.

Leighton Meester

#10 T.J. Thyne

Before he was bug expert Jack Hodgins on Bones, Thyne popped up as Jason Girard, a camper in 24 season 4 who stumbled upon the nuclear football in the wreckage of Air Force One and tried to help Jack keep it away from the terrorists.

#9 Darby Stanchfield

Before she was Abby, one of Olivia Pope’s Gladiators on Scandal, Stanchfield was Shari at the end of 24 season 4, the neighbor of Mandy the evil assassin who was blown up as a decoy.

#8 Connie Britton

Before she was a dramatic leading lady on Nashville, Friday Night Lights and American Horror Story, Britton was Diane Huxley, Jack’s girlfriend and landlord in his secret, off-the-radar life at the beginning of 24 season 5.

#7 Stana Katic

Before she was Detective Kate Beckett on Castle, Katic was Collette Stenger, an information broker for terrorists in 24 season 5.

Stana Katic

#6 Kate Mara

Before she was intrepid journalist Zoe Barnes in House of Cards, Mara played CTU analyst Shari Rothenberg, who replaced Edgar at the end of 24 season 5.

Kate Mara

#5 Harry Lennix

Before he was Assistant FBI Director Harold Cooper on The Blacklist, Lennix was Walid Al-Rezani in 24 season 6, director of the Islamic-American Alliance and the boyfriend of President Wayne Palmer’s sister.

Harry Lennix

#4 John Noble

Before he was Walter Bishop on Fringe or “Henry Parrish” on Sleepy Hollow, Noble got his start on FOX in 24 season 6 as Russian consul and terrorist accomplice Anatoly Markov.

John Noble

#3 J.R. Bourne

Before he was werewolf hunter extraordinaire Mr. Argent on Teen Wolf, Bourne played duplicitous forensic technician Connell Johnson in 24 season 6, causing drama between Milo and Doyle.

#2 Diego Klattenhoff

Before he was FBI agent Donald Ressler on The Blacklist or Brody’s Marine buddy Mike Faber on Homeland, Klattehoff played a U.S. Marine who oversaw prisoner Jonas Hodges in 24 season 7.

#1 Paul Wesley

Before he was Stefan Salvatore on The Vampire Diaries Wesley sank his teeth into the role of Stephen, Kim Bauer’s husband and the father of her child in 24 seasons 7 and 8, officially making him Kim’s only boyfriend who appeared in multiple seasons.

Paul Wesley

John Kubicek

Senior Writer, BuddyTV

John watches nearly every show on TV, but he specializes in sci-fi/fantasy like The Vampire DiariesSupernatural and True Blood. However, he can also be found writing about everything from Survivor and Glee to One Tree Hill and Smallville.