Other mistake: At The Boat explosion incident, when Roy and Johnny climb aboard The Boat Johnny says, "We'll set up the Biophone here," but subtitles read "We'll set up the platform here." Subtitles from Universal Studios 2010 DVD.
Other mistake: After Roy and Johnny get back to the station, when Johnny takes the container of milk out of the fridge, we can see the black tape around it covering the brand name. There's another container in the fridge with red tape covering its brand name as well.
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.