Man On The Moon is the story of the career of Andy Kaufman.
One of the personas that Andy sometimes adopted was Tony Clifton, an obnoxious and terrible lounge singer. Tony is an alter-ego for Andy. In early scenes, when Andy is not famous, audiences believe that Tony is what he appears to be; but later, when Andy is a celebrity, audiences understand that Tony is a character played by Andy.
In one scene, Tony is on stage before an audience, and audience are enjoying the performance as a satire of some sort, thinking that the "Tony" that they are seeing is really Andy in disguise. But then Andy joins Tony on stage. The audience IN the film, as well as the actual audience OF the film, are confused how this could occur. A few moments later the film discloses that when both Andy and Tony are on stage together, Tony is played by Bob Zmuda, a friend of Andy's.
As you might expect, Andy's funeral occurs fairly late in his career. We see the funeral in the film, and in the next scene we see crowds standing outside a theater, and the message "One Year Later" is superimposed. The crowds cheer as someone arrives in a limo and emerges, clad in tux and with a bag over his head, and enters the theater. Then we see (obviously) this same person perform the song "I Will Survive" on stage -- and it's Tony Clifton. Again the audience in the film is reacting happily as Tony does his performance. Since we just watched Andy's funeral we suppose that Tony is again being portrayed by Bob Zmuda. But then the camera moves around the room and we see Bob Zmuda in the audience.
What is this scene about? Are we supposed to understand that after all this is the real Tony Clifton, not played by Andy or Bob or anyone else? Did this event occur? Were this scene in the film, and the event it depicts, both supposed to feed rumors that Andy was still alive, as the choice of the song "I Will Survive" obviously suggests?
My hunch is that this scene does not correspond to any real event but was intended as the sort of scene that Andy would have wanted in the film, another attempt to bewilder the audience and destroy any understanding what is real and what is imaginary.