Continuity mistake: After Chet sees The Mouse run under the fridge, when the guys are discussing The Mouse Johnny's medical holster is clipped at his right hip, but when they're dispatched to 'man unconscious at laundromat' his medical holster is now at his left hip as he walks to the squad.
Continuity mistake: When Roy and John are at the nurses' station talking to Brackett and Dixie about The Old Engine, at the bottom right corner of the screen we can see the patient's metal clipboard chart being held, before Early even walks over to the nurses' station holding a chart. Then when Early does walk over he stands to Brackett's right, but in shots facing Dix and Johnny we still see that chart being held, where Roy is supposedly standing, not Early. Additionally, the charts hanging on the chart holder change/vanish between shots.
Continuity mistake: At the scene of the traffic accident involving the car and the armored truck, the chrome center of Squad 51's lightbar is backwards, the solid side is facing front and the vertical slats are facing the rear.
Continuity mistake: When Mrs. Evans complains to Dixie that she's been waiting two hours to have her cigarette burn taken care of, in her closeups her handbag strap is over her shoulder, but in wide shots her handbag is hanging from her arm.
Continuity mistake: Roy and Johnny are at the nurses' station discussing the problem of non-emergency calls for paramedics, then it cuts to Dixie in the waiting room, when a nurse asks Dixie if the ER can take a pediatric patient who needs treatment immediately, and Dixie tells her to go to Morton in treatment 3. Then when Dixie speaks to Mrs. Evans we see that young girl being brought to treatment 3. During the next two minutes while Dix walks up the hallway, she quickly speaks to Brackett, then to an impatient parent, then to that nurse again, then Brackett again, and finally to Roy. When Roy asks Dixie where Johnny is, Dixie tells him in treatment 3 (dubious how she would even know that fact), and when Roy walks in to get Johnny that pediatric patient who was just brought to treatment 3 is not in there, instead Morton is examining Wild Bill.
Continuity mistake: After Johnny and Roy get back to the station and find Bill, who's filling in for Chet, in the kitchen cooking Chet's awful stew recipe, the tones drop and Squad 51 is dispatched to "man unconscious." Just as the bay door opens we can see Engine 51 parked in the bay, but when the squad heads down the driveway the engine's now gone. This presents another problem, because if the footage shows the engine gone, then why is Bill still at the station cooking stew instead of being with the rest of the engine company?
Camera Bug - S4-E10
Continuity mistake: When Roy's using the Ambu bag on the unconscious teenager from the school fire, while the stretcher's being wheeled to treatment 3's door, Roy has a stethoscope hanging around his neck, but in the next shot as they enter treatment 3 the stethoscope has vanished.
Continuity mistake: When 51's with Cora, the woman who was thrown into the middle of a cactus patch, they lower the ladder horizontally so it's beside her for the rescue, but while Roy treks across the ladder in the next shot of Cora the ladder is nowhere to be seen, then when Roy reaches her we see that it's indeed right beside her.
Continuity mistake: When Brackett is talking to Roy and Johnny in the hallway outside treatment 3 about the guy who will likely lose his injured leg, Brackett is wearing a tie with a pattern, and when he walks into treatment 3 Brackett's tie is tied differently.
Continuity mistake: While Johnny and Roy are driving in the squad, they're dispatched to an 'unknown type rescue', and when they arrive at the incident which is a football player who kicked in his TV screen, Roy's hair is much shorter - note the front and sideburns. Then back in the squad it's the same length as earlier.
Continuity mistake: When Roy and Johnny are leaving the home of the football player who kicked in his TV screen, in the interior shot as they're walking out, Roy has a stethoscope around his neck and is holding the Biophone with his right hand and drug box with his left. In the next exterior shot, the stethoscope is gone and the drug box and Biophone have switched hands.
Continuity mistake: At the start of shift, after Captain Stanley gives the guys assignments, when the last shift rolls up in the squad, in the closeups Roy is suddenly holding his helmet while he and Johnny are talking to Dwyer, but it's gone again in the wide shot. When the squad is dispatched, Roy grabs his helmet which had been lying on the engine's running board in all the wide shots.
It's How You Play the Game - S4-E19
Continuity mistake: While Johnny tells the other guys that the losers of the baseball game, between 51 and 36, will have to pay for the entire cost of the picnic, Chet's eating an apple which has less eaten by the time he tosses it into the garbage.
Continuity mistake: After the OD is dropped off and left at the ER, during her examination Brackett finds the marks on her foot, and in the closeup the marks have moved and are more pronounced than in the wide shots.
Transition - S4-E15
Continuity mistake: When Gil's in the basket ride at the amusement park, while Captain Stanley swings the line that Johnny's hanging on, in the closeups the open cage door is facing Johnny, but in the long shot looking up the basket's open door is on the opposite side, and Johnny would not have been able to enter it as easily.
Transition - S4-E15
Continuity mistake: When Roy walks into the ER with the chemical burn patient they rescued from a kitchen filled with hydrogen sulfide, Dixie tells them treatment 1 which has a windowless door, but in the shot from inside the room the door has a window, and we can tell it's treatment 3 they're in.
Transition - S4-E15
Continuity mistake: After Brackett and Johnny try to convince Gil that he's not responsible for the MI patient's death, when Johnny walks out of the treatment room he says he's going to check on Roy, and as he opens the door we can tell that he's in the room across from the nurses' station. Then when he and Roy leave the treatment room where Early had examined Roy, we can see that it's the very same treatment room that Johnny had just been in with Brackett.
Continuity mistake: When Dixie tells Roy and John that Vic wants to see them the guys walk into treatment 2, but in the shot from inside the room we can see that they're actually in treatment 3, on the opposite side of the hall.
Continuity mistake: When Squad 51 is dispatched to the "possible assault victim," the address given is "743," but when John and Roy are at the scene the address on the house is 4015.
Continuity mistake: When Dixie walks over to the admitting desk and asks the nurse to stop what she's doing to set up treatment 4, the nurse places the black pen inside the metal folding clipboard and flips it closed, but in the next shot the pen is lying on top of the closed clipboard.
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.