Revealing mistake: After the two drivers from the traffic accident walk off holding hands, and Johnny tells Roy what happened with Barbara, while Roy explains "body-language" to Johnny, we can see the white tape with "Kevin" inside Roy's helmet.
Revealing mistake: When Station 51 is dispatched to 'fire in the salvage yard', in the exterior shot as the squad and engine roll out of the bay, we can see the real Station 127's vehicle is still parked inside the apparatus bay, near the rear bay door.
Revealing mistake: When the critical boy who ingested the ant poison is being wheeled into the ER's treatment 3, we can see Johnny laughing, and obviously since absolutely nothing about the situation is funny, we know it's Randolph Mantooth just cutting up during the take.
Propinquity - S3-E20
Revealing mistake: When Johnny and Roy are figuring out how to free the woman trapped in her wrecked car, the flames spread and Johnny's pant leg catches fire, but as he's trying to smother that flame, the strip of fire stunt gel that was smeared on his pant leg is visible.
Revealing mistake: When Johnny and Roy are in the squad heading to Rampart after freeing the girl's toe from the bathtub, they get dispatched to 'possible electrocution' and we can see the white tape with "Kevin" inside Roy's helmet. (00:37:30)
How Green Was My Thumb? - S3-E17
Revealing mistake: When Roy brings the man with a laryngeal obstruction into the ER and is taken quickly to treatment 1, his head is tilted back and Early places a laryngoscope into the patient's mouth and says that he sees the obstruction. The problem is that we can see that the laryngoscope is actually at the side of the patient's face. Then, when Early uses the forceps to remove the obstruction, once again we can see that it does not go into the patient's mouth.
Revealing mistake: After Gage gets bitten by the rattler, when the driver of Tractor 2 begins ascending the cliff, there is a nice close-up as he passes and this young stuntie is most certainly not the older driver seen in this scene. Not to mention the watchless driver suddenly acquires a black watch and a plastic face shield attached to the helmet.
How Green Was My Thumb? - S3-E17
Revealing mistake: When Roy brings in the man with the laryngeal obstruction (partial dental plate), Morton and Early meet them at receiving, then as they rush the stretcher into treatment 1, it's amusing to note that the treatment room across the hall (treatment 2) has room number 412 on it, and even better, treatment 1 itself has number 411 on its door. Obviously the set was prepped for the following shots, when Johnny follows the nurse onto the 4th floor.
Revealing mistake: When Cindy and her mother come to see the station, Cindy goes to the closet with the gear, and as she opens the door Cindy starts laughing before Johnny even gets hit by the phantom, and then she glances toward the camera grinning because of the prank.
Revealing mistake: When the guys are in the backyard with the woman who fell through the ground into an old abandoned well, in the overhead shot we can see the cuts that created the cutout hole on the flat surface around her, and that it's not really dirt or sand that she's slipping through.
The Promise - S3-E11
Revealing mistake: When Richard jumps out of the 6th floor window, in the interior shot we see that he lands right at the base of the window's frame, as his body bounces back from the impact, but when Brackett looks out the window Richard is lying on the ledge, which is much farther down than the window's bottom frame.
Revealing mistake: At the start of the episode, in the closeup shot of Chet, Roy, and Johnny as they're talking about their trip, we can see the Land Rover hood's base plate where the vehicle's spare tire is supposed to be mounted, but the tire isn't there because of the mounted camera facing the actors in the vehicle. In other shots the spare tire is properly mounted on the Land Rover's hood.
Revealing mistake: While 51's guys are on the roof of the construction accident, when Truck 8 rolls up on scene and then places its outriggers we can see the red vinyl material adhered to back of the engine, covering its real company number.
How Green Was My Thumb? - S3-E17
Revealing mistake: When Roy and Johnny are at the nurses' station with Dix, Roy decides to deliver the plant that was left for Mrs. Johnson so he and Johnny get into the elevator, and when Roy says, "Six," the floor indicator light on the control panel turns itself on before Johnny even presses the 6th floor button. That light would not turn on if someone up on the 6th floor pressed for the elevator.
How Green Was My Thumb? - S3-E17
Revealing mistake: After Johnny jumps into the wine vat, when he and Roy pull the drowning man out of the vat we can see the rubber/latex suit the man is wearing under his clothes, when his shirt is lifted up.
Revealing mistake: During Station 51's rescues on the foggy San Diego Freeway, when Chet is giving CPR to the little girl, it's just too obvious that he's not really giving CPR, unless her mouth is located on her cheek.
Revealing mistake: After Station 51 is dispatched to 'man trapped at the rock quarry', just before Squad 51 heads through the tunnel-like passageway, in the shot from the top of the squad we can see that the lightbar's chrome center and trim have been covered in black, presumably to prevent the reflection of the camera and cameraman, who's riding atop the squad.
Revealing mistake: While John's in the ambulance with the boy who ingested the poison, after John inserts the esophageal airway and uses the ambu-bag, just as John says, "Real good," if we look out the window behind the attendant, we can see Universal's GlamourTrams (a set of three trams) driving by in the distance. The footage inside the ambulance was shot while the ambulance drove around Universal's lots.
Revealing mistake: After the snakebite, when the guys carry Johnny and place him at the back of Engine 51, the chrome spotlights are shiny and reflective, but in the closeups the spotlight near Marco has been partially sprayed with a dulling spray, to prevent the camera's reflection.
Revealing mistake: At the structure fire, when Engine 9 and Engine 17 roll up, we can see the large, red, rectangular vinyl material that is adhered to the front of the engines, with their company numbers printed on it. Additionally, the red vinyl material adhered to the top of 9's and 17's cabs, which cover their real company numbers, flap up in the wind.
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.