Name of a movie

I saw a parody of it on the Simpsons once. It's where two teens are in an abandoned saw mill where there hasn't been a murder 10 years that night. the teens make out when the door bursts open and this person comes in with a running chainsaw. then the scene of the প্রদর্শনী changes to where the boy teen is asking a shrink if what he saw was a dream. Then the psychologist pulls out a running chain saw and starts to attack the teenage boy

if it helps, the Simpsons episode is where Bart meets a girl named Darcy অথবা 'Little Big Girl' is the title