There’s a rumour that F.W. Murnau’s classic vampire film Nosferatu features actor Max Schreck in not one but two roles. He is of course the vampire himself, but – the rumour goes – he also appears briefly in another role near the beginning of the film, as a clerk in the office where Hutter works. (Nosferatu was an unofficial adaptation of Dracula, and the character names were changed in an unsuccessful attempt to avoid incurring the wrath of Bram Stoker’s estate. Hutter in the film is Jonathan Harker in the novel; Dracula becomes Count Orlok.)
There’s a still of the clerk above, and of Schreck as Orlok below, and plenty more images of Schreck in and out of make-up online.
It’s a tricky one. The clerk seems to have Schreck’s height, his narrow shoulders, and certain mannerisms. There’s something similar about the area around the eyes, too. The clerk’s head looks more rounded in the still above, but as he lowers his face at the end of the shot, it takes on something of Orlok’s length, before being hidden (very pointedly) behind a large hat. The forehead seems different, but as Orlok this would be hidden by make-up or prosthetics, and the prosthetic teeth would lengthen Schreck’s face.
Ultimately, there’s nothing here to either provide a definite ‘yes’ or a definite ‘no’. The only source I can find for the rumour is on IMDb, under Nosferatu trivia, which is user-submitted, and so not really authoritative. A discussion on the boards there is indecisive, and raises the question of who added the fact and what their source was.