While many grew up hearing Michael Rosenbaum as the voice of The Flash on Justice League and Justice League Unlimited, the actor is arguably more well known on the DC block for his run as Lex Luthor on Smallville. Among his costars on the WB-turned-CW series was John Glover, who played Lex’s father, Lionel Luthor, whose parenting skills left much to be desired. In real life though, Rosenbaum and Glover are on great terms with one another, as evidenced by the former leaving the latter a sweet birthday message, which in turn prompted Glover to share the birthday love with a fellow DC legend.
