Visible crew/equipment: After Station 51 is dispatched to the fire at a singles club, when Engine 51 pulls into the parking lot it and then turns around, the reflections of multiple array lighting can be seen on the engine's surface and Mike's window when he opens the door.
Other mistake: When the self defense instructor tries to use Mrs. Pestone to demonstrate the flip, he puts his arm around her and covers her mouth, then it cuts to a shot of Squad 51 rushing down a street. This particular shot is from 5x8, "The Lighter-Than-Air Man," when Roy drives past the school kids and crossing guard.
Other mistake: During the singles club fire, after Johnny and Roy check the men's room upstairs, there's a shot of firemen in full turnout gear with hoses, and this footage is from the first season's pilot episode, "The Wedsworth-Townsend Act."
Other mistake: During the actual cliff rescue of the hang gliding accident victims, Roy and John are wearing hiking-type shoes with ridges on the soles, not their uniform shoes.
Pressure 165 - S5-E7
Visible crew/equipment: When Roy and Johnny are with Chef Michel, the outline of the mic transmitter can be seen on the front of Johnny's shirt.
It's How You Play the Game - S4-E19
Other mistake: After Chet says that he doesn't like when people expect too much of him, Squad 51 is dispatched to "man bit by an animal," and when Roy gets into the squad the highly reflective chrome spotlight has been sprayed with a dulling spray, to temporarily dull the surface.
It's How You Play the Game - S4-E19
Visible crew/equipment: When Johnny walks into the kitchen and gets the cold shoulder from Marco and Mike, and then when Chet walks in, the reflection of production equipment is visible on the oven's glass.
It's How You Play the Game - S4-E19
Continuity mistake: When Squad 51 dispatched to 'man bitten by animal', the center chrome on lightbar is a solid piece, but en route the chrome center is striped and its trim is covered with black tape. Then when they approach the car lot, the black tape is gone.
It's How You Play the Game - S4-E19
Visible crew/equipment: After Mike and Marco ignore Johnny as he walks into the kitchen, when Roy holds the chrome coffee pot and pours Johnny a cup of coffee, the reflections of the camera/lights are visible on the coffee pot's chrome surface.
Continuity mistake: While Roy and John are still aboard the Coast Guard helicopter during the cliff rescue at Catalina Island, when the chopper's on scene, in the overhead shot from inside the chopper, we can see where the victim is lying on the rocks, however, in the next shot from ground level, the victim is now lying on the other side of the jutting rock.
Continuity mistake: While Early, Morton, and Dixie are examining the young boy who fell, Early's wearing a gold ring (wedding band in real life) on his left hand's ring finger, but when Dixie finds the tick she asks Early to have a look, and in the closeup of the boy's head, Early's gold ring has vanished.
Continuity mistake: When Engine 8 is dispatched to "man unconscious at construction site," we see Engine 8 going past Curson Ave, then the next shot Engine 8 is driving up from the other direction of Curson Ave and passes it going the other way. Neither are flipped shots. Other than seeing the sign for Curson Ave, other giveaways are the same signs or parked vehicles.
Other mistake: When Squad 51 is dispatched to an 'unknown type rescue', as the squad rolls out we can see the Crown engine from the show's first two seasons parked in the apparatus bay, instead of 51's current Ward LaFrance.
Visible crew/equipment: When Roy tells Karen that she'll know when she can do it on her own when she'll have to, the reflection of set lighting is visible on the squad's chrome spotlight. Additionally, when Station 51 is dispatched to the structure fire the rear bay door closed, but when the rigs roll out the rear bay door is open.
Other mistake: When Station 51 is dispatched to the landslide, the engine company get into their turnouts and roll out, but in the next exterior shot as the engine drives past the camera, not only are the guys not in their turnouts, it's too obvious that none are 51's guys, and the one in Chet's jumpseat even leans forward. Presumably they're 127's guys. Also the light bar on the squad and the rotating light on the truck are not on.
Other mistake: When Station 51 is on scene at the landslide, there's a dresser on the grass in front of the house, and when the explosion occurs due to the broken gas main, in the closeups as Johnny dives to the ground there's what looks like a can of gasoline (used for the stunt perhaps) atop that dresser that wasn't there before, and it's also not in the wide shots as Johnny dives down.
Visible crew/equipment: After Roy and Johnny speak to Chet's friend the realtor, when Station 51 is being dispatched to the accident on Harbor Freeway, in the overhead shot of the apparatus bay, we can see the shadow/reflection of production equipment moving on the engine's windshield.
Visible crew/equipment: When Station 51 is dispatched to the rescue on Johnson Canyon Bridge, just as Engine 51 rolls out of the apparatus bay, the reflection of array lighting and two reflector screens are visible on the engine.
Revealing mistake: While the squad and engine are en route to "possible fire", one of the camera angles is from the POV behind Roy and John, where the back of squad is located. That’s fine, but the problem is that there's bright sunlight on their backs as they’re driving, when it should not be there. Artistic license is acceptable, but with so much sunlight where it should not be it reveals that Squad 51 is not in its normal state.
Above and Beyond... Nearly - S5-E20
Visible crew/equipment: In the dental clinic, when the possible MI is being examined, two actors' black tape marks become visible under the patient's chair, one below the footrest and another below the headrest.
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.