Continuity mistake: During the first two seasons of the show, when Engine 51 and Squad 51 are dispatched, sometimes one or both vehicles change their appearance when they leave the firehouse, while en route, or when they reach their destination. Note the hood, lights, etc.
Revealing mistake: When Squad 51 is dispatched from the stationhouse, the exterior shots show buildings, traffic, trees, etc., they pass along the way. In some close-up shots of Gage and DeSoto while en route, too much of the vehicle's left and/or right sides are visible, which actually shows nothing but a blank screen behind them.
Continuity mistake: When John first explains how to rescue the little girl in the hole, he wraps his left hand around his right wrist, but in the next shot it's his right hand that's around his left wrist.
Continuity mistake: The shaving foam on DeSoto's face changes between the face-on shots and the reflection shots, and in the reflection he shaved from cheek to chin, but in face-on shots only to the neck.
Continuity mistake: When DeSoto starts to crack about what's upsetting him, Gage places a mop beside another mop, up against the door and it falls over. Next shot both mops are upright and in different positions as well.
Continuity mistake: On the front end of Squad 51's hood, the letters of the word 'DODGE' appear either in silver or in red, or sometimes it's not there altogether.
Visible crew/equipment: When the guys are wearing their helmets, multiple head set lights are usually reflected on the black surface, more often than not.
Inventions - S3-E22
Visible crew/equipment: On site at the chemical leak, when Captain Stanley talks into his handie-talkie and says "Engine 36, we're not doing any good with this, let's try light water," in the next shot, while the camera pans to the right, we can see a cameraman (filming Deluge 105's closeups that we see during this scene) holding his handheld, standing in front of an engine and facing Deluge 105, just before the camera focuses on the guys with the hoses.
Other mistake: When Roy gets off the phone and heads to the squad, Johnny follows him wanting to know who he was talking to, and after Roy tosses Johnny a rag to help wipe down the squad, we hear the dispatcher ask, "Foam 27, what is your location?" but subtitles read, "Phone 27, what is your location?" Subtitles from Universal Studios 2010 DVD.
Other mistake: While 51's guys are at the accident scene by the freeway on-ramp, when Roy's standing on the ladder and says the car door's jammed, Captain Stanley tells Chet and Marco to get the Porta Power, but subtitles read "Jack, Marco, we need the Porta Power," even though there's no character named Jack. Subtitles from Universal Studios 2010 DVD.
Other mistake: When Early and Morton are examining Johnny, Early points out Johnny's torso as he says, "Mike, you see this bruise?" but the subtitles read, "Frank, you see this bruise?" A couple of minutes later the subtitles get Mike's name right. Subtitles from Universal Studios 2010 DVD.
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.
The Wedsworth-Townsend Act - S1-E1
Visible crew/equipment: When 127's snorkel is raised to rescue the man who was electrocuted atop a utility pole, as he's being loaded, in the first closeup within the snorkel, we can notice two things. We can see someone wearing denim at the left of the screen between 127's guy and Johnny, and we also see the ground past Johnny's head. Then as the snorkel is still being lowered, in the shot from the same POV, once again at the left we see that crew member wearing denim, who is outside the snorkel basket, and also see the ground, but the ground has not changed. This reveals that these two closeups were shot at ground level.
Welcome to Santa Rosa County - S6-E10
Visible crew/equipment: Right after rescuing the two injured climbers, when John and Roy are in the back of the pickup truck with them, just as the pickup drives off to follow Sheriff Bittner's squad car, we can see the reflection of crew and the camera rig on the Land Rover's windows.
The Lighter-Than-Air Man - S5-E8
Visible crew/equipment: When Crockett leaves Medford's room with the glass that Medford drank from, there's a mirror over the sink, and in the mirror's reflection we can see the camera's moving shadow on the wall, right beside Crockett's reflection.
Revealing mistake: At the site of the hang gliding accident, just after the glider falls, in the long shot when Johnny and Chet pull the unconscious victim higher on the cliff, the victim is supposed to be unconscious, yet we see him use his right leg to push himself higher up to help John and Chet pull him up.
Other mistake: While John is searching through the papers for the receipt, when Roy takes the milk carton out of the fridge he pours some into a glass and some ends up spilling onto the floor, we can see there's black tape on the milk carton covering the brand name.
Visible crew/equipment: At the refinery fire, after the stokes is loaded onto the snorkel and then John and Roy climb in, two shots after Captain Stanley's closeup, in the shot tilting up at the descending snorkel basket, a crew member who is crouching down can be seen on the tower behind it (presumably it's the second cameraman shooting all the footage from that angle).
Continuity mistake: When Johnny is being examined by Dr. Early and Dr. Morton, Roy is in the treatment room with them, and he's not wearing a watch, but when Roy steps into the hallway and speaks to Chet he's suddenly wearing a watch.
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.