"There is going to be a cameo by a classic Superman movie actor in Man of Steel.
What do I mean by ‘classic’? I mean that the actor could be anyone, alive or dead, who appeared in any (not all) of the Superman movies from 1948 to 1987 and 2006′s Superman II: The Richard Donner Cut".
A YouTube video clip, upon close examination, shows a resemblance to the Clark Kent character from the original "Superman 3" movie. The hat, the suit, the satchel all iconic props. This took place in a bike riding scene with Henry Cavill while filming for "Man of Steel" and when they start rolling, he rides by the "mysterious stranger"
Of course, this hasn't been the only time rebooted movies featured cameo appearances of stars/characters from the original movies. For instance, the aging ape in Tim Burton's "Planet of the Apes" reboot was played by Charlton Heston.
Noell Neill, who played Lois Lane in the original T.V. series from the 40's and 50's made her appearance in "Superman Returns".
So, it would be more than likely to happen again in "Man of Steel".