Despite claiming he was cut from the movie, Seth Green does appear in it, although it is just for three seconds, and for two of them he is seen from behind. He is the short red-haired vampire that gets kicked by Buffy outside the gym when a group of vampires, including him, are taunting her. You can recognize him by his haircut alone.
Screenwriter Joss Whedon found Donald Sutherland extremely difficult to be around. Sutherland re-wrote most of his dialogue and scenes, often making the scenes incomprehensible in Whedon's opinion. Whedon praised Sutherland's abilities as an actor, but called his behavior "rude", and Sutherland himself "a dick".
Joss Whedon maintains the movie should be considered stand-alone, and that any of the events, characters or character traits in the movie, should not be referred to as canon for the television series of the same name.
In the original version of the script, Merrick committed suicide, to escape being turned into a vampire by Lothos, who wanted to know the Slayer's identity, so he could dispatch her. It is this version that was restored in the Buffy "Origin" comic.
The original script by Joss Whedon was heavily re-written to make the film "lighter". In the original script, Buffy burns down the school gym that the dance is being held in, in an effort to destroy the vampires. In the television series (Buffy the Vampire Slayer (1997)) this fact is referred to several times, as the series is seen as a spin-off of the original, unproduced screenplay, rather than this film.