Based in part upon a legend that Max Schreck was in reality a vampire which is why he played the role of Orlock/Dracula so well. Some variations of the legend suggest that Nosferatu (1922) was the only film Schreck made, though in reality he was already a stage and screen veteran by the time Nosferatu was shot, and would appear in many non-Vampiric roles before his death in 1936.
The locomotive that conveys the film crew to Czechoslovakia is named "Charon". In Greek myth, Charon was the ferryman who conveyed the souls of the dead across the river Styx.
It was utterly impossible to film at night in 1922, so all night-time scenes were actually filmed in broad daylight. Originally, these scenes were tinted blue in order to differentiate them from those that were supposed to take place by day.
At the beginning of the movie one of Murnau's assistants calls him one of the greatest moviemakers ever, with D.W. Griffith and Sergei M. Eisenstein. In 1921 Eisenstein had not yet directed any movie (his first movie is from 1923).
After they film Gustav entering the castle, he is talking in the doorway with Murnau and Grau. Murnau and Grau then walk into the courtyard where Gustav is already waiting for them.
F.W. Murnau: Ladies and gentlemen, this is Max Schreck, who will be portraying our vampire, Count Orlock. As you no doubt have heard, Max's methods are somewhat... unconventional, but... I am sure you will come to respect his artistry in this matter.