Revealing mistake: During the rescue at the jail, while Roy tries to get a safety belt around the prisoner's waist, the man freaks out, then grabs Roy and they both swing out on Roy's safety line. When the camera pans a bit too far to the left, we can see the edge of the fake "sky" screen on the left, behind the building's replica set used for closeups.
Revealing mistake: On the roof of the jail, Roy buckles his safety belt around his waist, with an extra belt for the prisoner hanging from it as well. When Roy removes the second belt from his own, we can see two carabiners that are now attached to his lifebelt, which go down into Roy's pants. Those carabiners are presumably attached to extra support under Roy's pants.
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.