What are some examples of an actor too old to play a role?

You probably have heard that people in Hollywood like to cast older actors to play younger people. Don’t know why they don’t go with an actor of that age but hey this is entertainment kids. I wanna know what some great examples of this are. 3 that come to mind. Luke Perry being 23-30 playing a high school turned college student. (BH90210). Scott Baio still being 30 years old never having graduated college. (Charles In Charge). Lucas Till being 26 years old playing a high school student (Monster Trucks)