For the second film, Christopher Reeve and Marlon Brando shot one scene together in person. The scene was later cut, but restored on the 2006 DVD release of “Superman 2: The Richard Donner Cut”.
Everybody going into the project knew Marlon Brando would get top billing, as he was well known, and Reeve was basically an unknown at the time.
According to an interview with Christopher Reeve, Brando took him aside one day on set and said, “Kid, I may get top billing on this, but this is YOUR movie. Take it!”