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.
Max Schreck (Willem Dafoe) recites Tennyson's poem 'Tithonus' at one point: 'The woods decay, the woods decay and fall, the vapors weep their burthen to the ground...' This is apropos, because the poem is about a character from Greek mythology who was immortal even though he continued to age. Just like Schreck, this made him a tragic figure.
Murnau's line, "If it isn't in the frame, it doesn't exist", is a paraphrase of a piece of advice the real Murnau gave to the young Alfred Hitchcock when the latter visited the Ufa Studios in Berlin before becoming famous. Hitchcock never forgot this advice and was still quoting it when making his final movie in the mid-1970s. The use of the quotation in the context of "Shadow Of The Vampire" is a distortion of what the real Murnau meant.
Just prior to the crew's arrival at the castle for the first night of filming, a quick establishing shot depicts Count Orlock (disguised as a carriage driver) arriving at his castle with Hutter. This was a scene edited from the original Nosferatu featuring Max Schreck and Gustav von Wangenheim.
The trivia item below may give away important plot points.
Originally titled "Burned to Light" in a reference to the filmmaking process (and the vampire's ultimate fate in the film); the title change came about because apparently some people misread the title as "Burn Ed to Light."