Other mistake: During the fire at the horse ranch, when Engine 40 rolls up we can see that the engine company's number is covered atop the cab, and the large, red rectangular vinyl material that's adhered to the back of the engine with nothing on it. Presumably covering the real engine company's number.
Other mistake: When the dispatcher sends Squad 51 to the heart attack at the bank robbery location, the address is given as "2057 North Hillcrest, cross street Barker," but when they arrive at the corner bank, the sign reads Celis Street.
Continuity mistake: After John spots a cute nurse talking to Dixie, when he zeros in on Dix for the nurse's name Dixie's holding a pad in her left hand, but in the next closeup her left hand's empty as she gives John an entire run-down on that nurse.
Audio problem: After Johnny gets out of the elevator, Johnny sees a crowd around the treatment room, so Roy tells him that they're interviewing the bank guard who was shot, and when we hear Roy ask, "How'd you make out with the girl from orthopedics," his mouth is saying something different.
Continuity mistake: When Dr. Early and Marcia's father stand outside her semi-private room, number 104, we see treatment 4 is right beside it. There are two problems with this bizarre situation. First, when Dixie gave Early the lab results about Marcia's possible pregnancy earlier, treatment 2 is right beside treatment 4, not the semi-private room 104. Second problem is that when Early and the parents walk into Marcia's room, in the interior shots we can see that there's a perpendicular wall right beside the doorway to its left, where the hallway ends. (00:19:20 - 00:31:30)
Visible crew/equipment: When Station 51 arrives at the salvage yard's fire, Johnny gets out of the squad, and when he puts on his turnout coat as the camera zooms out, a dark haired crew member wearing a short sleeve white shirt is visible at the lower right corner of the screen.
Other mistake: When Station 51 is dispatched to the woman who fell through the ground into the abandoned well in her backyard, en route there's a moving bird's-eye view as the filming chopper follows 51's vehicles making a right turn. On the ground below, there are two people standing beside a blue station wagon, and one points up to the filming chopper flying overhead.
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.
Other mistake: When the dispatcher sends Station 51 to 26309 Barcelona Drive, as the squad pulls up in front of the house, the number on the mailbox post reads 4050.
Other mistake: At the end of the episode, when Roy, Johnny, and Chet are at their lockers, Roy comments that Gloria won't make the same mistake twice about the $8.42, and Chet laughs, but the subtitles read, "Marco laughing", even though Marco is not in the scene. Subtitles from Universal Studios 2010 DVD.
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: While the guys are at the table eating Marco's stew, when Johnny remembers that he spent $8.42, numerous set lights are reflected on the coffee pot's chrome surface.
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.
Continuity mistake: When Brackett's examining the teenager (Donny Most) with paralysis Morton's standing beside him, but in the next shot as Dixie takes the teen's BP, we see Morton standing behind the teen with the student nurse, then Morton's back beside Brackett.
Continuity mistake: At the station, after Johnny has searched through a bunch of papers for the receipt for $8.42, when he gathers them up a yellow paper falls to the floor at his feet, just before Roy suggests putting them in alphabetical order. Then after Johnny stuffs the papers in an envelope and tosses the envelope in the garbage, the paper that fell on the floor has vanished.
Visible crew/equipment: When Johnny and Roy are with the woman who slipped down into an old abandoned well, the outlines of the lav mic transmitters are visible on the sides of their shirts - Johnny's at his left and Roy's at his right.
Visible crew/equipment: After Squad 51 is dispatched to a "man locked in a safe", when Johnny exits the squad and later when he gets back in, the outline of the lav mic transmitter is visible on the back of his shirt.
Continuity mistake: When Squad 51 is dispatched to a "man locked in a safe", at 1817 South Maplemoor, after the escape artist lets himself out of the safe, when Roy and Johnny head back to the squad the house address reads 4017.
Visible crew/equipment: On scene at the two vehicle accident, when Roy and Johnny are tending to the teenagers in the overturned car, the outlines of the mic transmitters and wires are visible on the sides of their shirts.
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.
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.