Enforced Method Acting: Justin Long and Gina Phillips didn't see the Creeper truck for the first time until they were on-set. In addition, Jonathan Breck made sure he didn't meet either of them until they were all on-set together.
Reality Subtext: Victor Salva, the director, was later arrested for performing sex acts on underage boys. The first film in particular makes for a much different watch with this knowledge.
The Other Darrin: Minor example, the Creeper in the last scene of the movie is actually Justin Long, not Jonathan Breck.