Revealing mistake: After Johnny joins Roy in the ambulance and the patient flatlines they continue to Rampart, and when Brackett asks 51 for a strip, if we look out the window that's beside Johnny, we can see GlamourTrams in the distance. And when Roy says, "Isopeterenol drip, 10-4," we can see GlamourTrams right outside the window. They are driving around Universal's lot while shooting the footage inside the ambulance.
Revealing mistake: After the MI patient from the construction site is brought to treatment 1, when Early uses the laryngoscope for an endotracheal intubation, we can see that he merely places the laryngoscope at the side of the man's face, especially since we can still see the entire distal end beside the man's neck.
The Tycoons - S5-E23
Revealing mistake: After Roy and Johnny get to the hospital with the 18 month old baby who stopped breathing, when Johnny is rushing up the hallway giving mouth-to-mouth to the baby, we can see that the happy little baby is wide awake and even smiling.
Revealing mistake: When Station 51 responds to the traffic accident, after Captain Stanley hands Johnny the Ajax tool, in the closeup it's obvious that the hands are not really Johnny's. Then there's another shot of the real Johnny, but once he removes his goggles, interestingly it's the stunt double who's in the following shots by the car, even when Johnny cuts himself, it's the stunt double.
Involvement - S5-E19
Revealing mistake: The former head nurse is supposed to be unconscious when she's picked up from the couch. Yet she puts her hand up on a shoulder when being carried out.
Revealing mistake: When Engine 8 rolls up on scene at the warehouse fire, as it passes the camera in the overhead shot we can see the real company number 60 printed on the surface between the jumpseats.
Above and Beyond... Nearly - S5-E20
Revealing mistake: Dixie and Brackett rush onto the elevator with a crash cart to go up to the third floor, for a possible MI in the dental clinic. The camera's POV is from the elevator, and in one continuous shot, without cutting away, we see the ER hallway through the open doors, then the doors close and in a few moments the doors open on the third floor. Even though the set has changed a bit, we can tell it's still the ER hallway by things such as the same scuff marks on the floor, and we can also catch a glimpse of the paramedic status board on the wall, where the base station room is located.
Revealing mistake: At the house fire, after Roy and Johnny go upstairs to rescue the invalid woman, Captain Stanley and Chet head to the front door, and just before Cap kicks in the front door, we can see that the door isn't actually closed, it's just ajar.
Revealing mistake: When Station 51 is dispatched to 'man trapped', just as Engine 51 rolls out of the apparatus bay and heads down the driveway, the real 127's vehicle is seen parked inside the bay, near the rear door.
Above and Beyond... Nearly - S5-E20
Revealing mistake: When Roy and Johnny are on the cliff loading the unconscious victim onto the stokes, as they try to lift each of the victim's legs, we can see the unconscious man also lifting his own leg to assist the actors.
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.