17 Again/YMMV

Unless they let both the principal and the kids in on the secret, isn't there a risk that somebody will call the police to report a teenager's disappearance ? And in that case, wouldn't Stan be a prime suspect ?
 * He Really Can Act: Zac Efron.
 * Fridge Logic:
 * Why would it take Ned seeing a picture (that he saw everyday, mind you) of his lifelong best friend to recognise that friend's younger self? Especially when Mike's wife see's the resemblance straight away. Easy, it's a simple case of Rule of Funny and having an excuse for a lightsaber duel.
 * How are they going to explain the disappearance of "Mark" ? It would normally be easy to just say he transferred away but:
 * Mike's kids both like him (although for different reasons) and know Ned, his "father", so they might ask to see "cousin" Mark.
 * Ned is now dating the high school principal, which means there is no way to conceal "Mark" non-existence if that relationship is going to last the way it is implied it will. "What happened to your son ? You know the one we met over when you enrolled him in my school ?"
 * Fridge Brilliance: Why is a middle aged guy that used to play basketball in high school still so good? Because with how bad his life is, and how he looked back on high school as his glory days, it is entirely conceivable that he practiced every day.
 * Older Than They Think: The film seems to be an unoffical(?) remake of a little known Disney film Young Again, starring Keanu Reaves. A middle-aged man named Michael Reilly laments his wasted youth and gets a visit from a mysterious old man who makes him 17 again. Most of the plot points, events and characters are identical.
 * Tear Jerker -- When Mike reads Scarlet his "letter".