sentences:  The seventh season comprises 20 episodes and concluded its initial airing on May 15, 2008, marking the second season to air on The CW television network.Regular cast members during season seven include Tom Welling, Michael Rosenbaum, Kristin Kreuk, Allison Mack, Erica Durance, Aaron Ashmore, Laura Vandervoort, and John Glover.In addition to bringing in new regular cast members this season, the "Smallville" team brought in familiar faces from the Superman media history, old villains from the show's past, as well as new DC Comics characters Kara Zor-El and Dinah Lance.