Visible crew/equipment: During the first encounter of the "Cool Rider" the police show up and he jumps over the car. In the rear shot, you can see the ramp on the ground under the police car that the stunt man used to jump the car.
Grease 2 (1982)
1 visible crew/equipment mistake - chronological order
Directed by: Patricia Birch
Starring: Michelle Pfeiffer, Maxwell Caulfield, Lorna Luft, Maureen Teefy
Other mistake: The movie starts in September 1961 and we are told that the talent show is in June. During the talent show there's a big banner saying 1961 when it should read 1962.
Principal Mcgee: If you play an instrument, remember, it is better to play with a group then with yourself.
Trivia: The character of Brad is played by Matt Lattanzi, the future husband of Grease star Olivia Newton-John.
Answer: I don't think it is ever mentioned as to who played the two nuns. I think they're just extras.