Propinquity - S3-E20
Visible crew/equipment: At the abandoned refinery, just after Roy attempts to pull out the man pinned under a tank, but is unsuccessful the first time, when it cuts to Captain Stanley and Chet, who are on the third level hosing the fire through the doorway, at the left of the screen a crew member is visible, watching them.
Propinquity - S3-E20
Revealing mistake: When Johnny and Roy are figuring out how to free the woman trapped in her wrecked car, the flames spread and Johnny's pant leg catches fire, but as he's trying to smother that flame, the strip of fire stunt gel that was smeared on his pant leg is visible.
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.