But that doesn't mean the main cast got along with every guest star ... Michael Rosenbaum broke down what went down in episode 2 of season 4 of Smallville with his former co-stars, Tom Welling ...

in Smallville during its first season, before he joined as a main cast member from season two to eight. And to many fans' delight, he returned for a few appearances in the final season of the show.

After Smallville, Allison was cast in a recurring role in the second season of the sitcom Wilfred and guest-starred as a policewoman named Hilary in an episode of the thriller The Following.