Ain’t It Cool have a very cool video showing the process used to create a three-dimensional Marlon Brando for Bryan Singer’s Superman Returns, using the old footage from Richard Donner’s 1978 movie. While you have to suspect there would have been simpler ways to achieve much the same effect, it’s still pretty nifty.
Brando was used in the original Superman as a sort-of ready made icon of gravitas and respectability (in a film that was, frankly, not that good, and therefore needed help in that regard). Singer obviously wants to harness that same aura.