Visible crew/equipment: When Roy and Johnny climb up the open drawbridge, just as they reach the top and see the car dangling off the edge, when Roy says "Boy," the second cameraman is visible behind Roy sitting on the bridge.
Visible crew/equipment: When Roy and Johnny are trying to get the basketball player (Kareem Abdul-Jabbar) out of the car, and when Roy exits the car to get equipment, the outlines of the mic transmitters and wires are visible on the back, left side of Johnny's shirt, and back, right side of Roy's shirt.
Visible crew/equipment: After Chet suggests to Johnny and Roy that they trade vehicles, as the camera pans out the reflections of crew and equipment are visible in the two hubcaps of Roy's car.
Other mistake: During the rescue at the top of the open drawbridge, in the shots of Engine 2 we can see the red, vinyl material with the company number imprinted on it, adhered to the front of the engine.
Other mistake: When Station 51 is dispatched to 'man trapped in vehicle', we can see the real Station 127's vehicle is still parked inside the apparatus bay, near the rear bay door.
Deliberate mistake: During the rescue of the car at the top of the draw bridge, The Boat approaches and radios in to say that they have a diver standing by. Then after Johnny shouts, "Are you all right?" the rescue boat is shown again, but this time it's a flipped shot - note that everything is reversed from the prior shot.
Visible crew/equipment: After the rescue on the draw bridge, when Squad 51 gets back to the station Roy goes to the backyard and sits in the sports car, and in this shot just as we hear Johnny's footsteps, on the Land Rover's window we can see the reflection of a crew member who is moving backwards.
Visible crew/equipment: When Johnny and Roy are at the top of the open drawbridge, beside the car hanging over the edge, just after Roy says "Be careful, this could go at any minute," the moving shadows of the cameraman and another crew member are visible on the bridge surface. That shadow is visible in two other previous shots from the same angle.
Continuity mistake: When 51's guys are at the table eating and discussing Roy and Johnny's deal, Johnny tosses his car keys to Roy, and in the following shots those keys vanish and reappear on the table repeatedly, and in the shots where the keys appear on the table, it's the ketchup, mustard, and napkins that have vanished. Also notice that the ketchup's brand name is covered.
Deliberate mistake: When O'Brien shows up at the nurses' station for Dixie's answer, after she declines the offer Dixie walks off to a patient who's brought in by the police, and the last closeup that's shown of O'Brien is flipped - note his hair is parted the opposite way and the background is backwards.
Revealing mistake: When Johnny and Roy are at the top of the open drawbridge, Johnny is wearing a watch on his left wrist, but when his stunt double rescues the woman in the car dangling off the edge, he is not wearing a watch. Additionally, the stuntman's pompier belt has a large axe sheath attached to it, but Johnny's life belt does not, and the stuntman's arms are much hairier, as usual.
Camera Bug - S4-E10
Plot hole: At the end of the episode, when Johnny tells the guys that he sold one of his photographs for $25, Chet claims the money is his and points to everyone in the photo, noting that Captain Stanley, Marco, Mike, Roy and Johnny are all in the photo but Chet's not, which means he's the one who actually used the camera and snapped the photo. However, the itty bitty problem here is that earlier in the episode, during the rescue, we can see that after Marco heads up the hill that it's actually Chet who's with Mike, Johnny, and Roy carrying the victim up the side of the hill, alongside Captain Stanley. So the only one who could have really taken that photograph was Marco, which completely contradicts the whole bit at the end.
Camera Bug - S4-E10
Revealing mistake: When they wheel the stretcher with the unconscious teenager from the school fire into treatment 3, the stretcher is pushed up against the ER's gurney, and when the teen's right arm gets caught between the stretcher and gurney, the supposedly unconscious teen moves his arm up out of the way. Then he lifts his left hand when the attendant removes the blanket.
Camera Bug - S4-E10
Other mistake: When Engine 51 and Squad 51 first roll in during the school fire, we see the burning building has a flat roof. After Johnny and Roy have rescued the unconscious boy from the classroom, there is a closeup of two firemen standing on a slanted, tiled roof with a hose, which is from episode 3x2, "The Old Engine", just before 17's Captain Harmell falls through the warehouse roof.
Camera Bug - S4-E10
Visible crew/equipment: After Johnny snaps the picture of Marco on the engine, when he prods Chet to go stand by the map, as the camera moves to the left we can see the reflection of production equipment/crew on the back of the squad, and we can even make out the shape of someone seated on a director's chair.
Camera Bug - S4-E10
Visible crew/equipment: When the stretcher with the unconscious teenager from the school fire is wheeled into the ER, while Roy is using the Ambu bag, just before they reach treatment 3 we can see the top of the set down the hall, near the nurses' station.
Camera Bug - S4-E10
Other mistake: While Roy and John are at 68's, Roy goes to the stove to see what Bob was cooking when he started having pain, and the closeup footage we see of the pot of bubbling chilli is the same as some of the footage of Chet's chilli in 4x1, "The Screenwriter," when 'Miss October' stops by the station.
Camera Bug - S4-E10
Other mistake: At the end of the episode, when Johnny's telling the other guys that his photograph was bought, the box of cereal and carton of milk that are on the table have tape affixed to them, to deliberately cover their brand names.
Camera Bug - S4-E10
Visible crew/equipment: At the accident scene with the truck carrying dynamite, when Roy is leaning over the driver's door, the outline of the mic transmitter is visible on the back, right side of his shirt. Then, when they're carrying the driver to the top, Johnny's becomes visible at his left side.
Camera Bug - S4-E10
Visible crew/equipment: When Johnny is driving Roy nuts by taking closeup pictures of him checking the squad's engine, the outline of the lavalier mic wire is visible on Johnny's back.
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.