School Days - S2-E14
Revealing mistake: While 51's on scene at the traffic accident involving a car that broadsided an ambulance, when Chet opens the back door of the overturned ambulance the license plate reads "99923U" but the "U" is lopsided and pushed to the edge of the plate, which makes it obvious that it's a magnetized letter. It's positioned properly in following shots.
Answer: I believe you are speaking of the old man, Mr. Wilson. He's played by J. Pat O'Malley.
Bishop73
Correct, it was J. Pat O'Malley...he also played the grandfather with his grandson when their rocket exploded, and also played "Old Bill" in the episode with Ann Prentiss, where Gage saves the little girl from the burning tree house, and her mother falls in love with him.