"Transformers" and "Las Vegas" star Josh Duhamel came back to "AMC" in the show's Aug. 4 and 5, 2011, episodes. His three-year run on the show ended in 2002 when his character, Leo du Pres, plunged into a waterfall. His body was never found so he was able to return this season to wrap up his relationship with his wife, Greenlee, played by Rebecca Budig before the series' end. (ABC News)