Above and Beyond... Nearly - S5-E20
Other mistake: After Dixie gets the call from the dental clinic about the possible MI, she and Brackett take the elevator located at the nurses' station and head up to the dental clinic on the third floor. Problem is that the ER is only a 2-storey building, so that is quite impossible.
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.