Amanda Wyss, who played the fifteen year-old Tina, was twenty-four at the time of filming.
Lampshaded when a sleep deprived Nancy looks herself in the mirror and says "Oh God, I look twenty years old". Indeed, if Heather Langenkamp wasn't yet past her 20th birthday when that scene was shot, it was, at most, a few weeks away.
Enforced Method Acting: In the final scene, the roof of the convertible came down much harder and faster than the actors expected; their startled reactions are real.
Executive Meddling: Craven originally wanted to end the film with a Happy Ending. However, Robert Shaye insisted on a darker ending and prevailed. This might have been for the better, since aside from opening the door for the very popular sequels to be made, Craven's intended ending was notoriously anti-climactic when judged against the rest of the film. Whether the ending was changed to allow for sequels, or to make the ending more exciting is a point of contention. Craven asserts the former, but Shaye has adamantly insisted on the latter in more than one interview.
It Will Never Catch On: It took about five years for Wes Craven to get funding for the film, because no one in Hollywood thought it was scary.
Ripped from the Headlines: Not only the reasoning behind changing Freddy from a child molester to a child killer (as detailed below), but also one of the sources of inspiration for the movie: Wes Craven has cited reading articles in the LA Times about children of Cambodian refugees who suffered from horrifying nightmares, refused to sleep and eventually died in their sleep after experiencing the nightmare a second time, a condition known as Sudden unexplained death syndrome, as inspiration for the basic idea of the movie.
Johnny Depp wasn't planning on auditioning, but he accompanied a friend to the auditions and was asked to read for a part and got cast.  would later go on to play Freddy himself some 30 years later.
A deleted scene revealed that Nancy and her friends all had siblings Krueger killed, either when they were too young to remember them or before they were born, making his death even more of a case of It's Personal. In fact, Marge admits that when Krueger burst out of the boiler room covered in flames, she was the one who killed him for good by shooting him in the head.
Glen's body was actually supposed to emerge out of the bed during the blood geyser scene.