Visible crew/equipment: After Chet is brought to the ER, Gage goes to the nurses' station. When Brackett opens the door and walks out of the base station booth, the actor's T-mark is visible on the floor behind him.
Visible crew/equipment: When Brackett's helicopter takes off the filming helicopter can be seen through the window. (00:03:45)
The Lighter-Than-Air Man - S5-E8
Visible crew/equipment: When Johnny brings in the box and Chet removes the wrapping for the baby layette, note the unfinished set wall past Engine 51 in the apparatus bay, which we can see since the front bay door is open, but when Captain Stanley walks in telling John about the phone call, the front bay door is now closed, then when the tones drop that set wall can be seen once again.
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.
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.
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.
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.
The Girl on the Balance Beam - S5-E18
Visible crew/equipment: When Brackett and Morton go to the outdoor eating area to speak with Nancy's father, just as Brackett sits down and crosses his legs, the actor's T-mark is visible on the floor in front of his chair.
Visible crew/equipment: During Johnny's surgery, the top of the set is visible over the door area when the camera angle tilts up, just before Morton comments that there's blood and wonders where it's coming from.
Visible crew/equipment: At the station, when Johnny and Roy talk about The Stewardess and then while Chet is mopping the floor, the bulging outline of the mic transmitter is visible on the front, left side of Roy's shirt, above his belt.
Visible crew/equipment: After Roy is electrocuted and falls from the second floor window, when Karen runs over to him and starts CPR, the bulging outline of the mic transmitter is visible on the back of Karen's white uniform.
Visible crew/equipment: After Karen, the new trainee, goes to the waiting room to speak to the elderly patient's wife, when Dixie walks over to Roy and Johnny to ask how she's doing, the outlines of the mic transmitter and wire are visible on the back of Dixie's white uniform.
Visible crew/equipment: In the ambulance, when Roy administers the bicarb and then the isoproterenol IV, the outline of the mic transmitter is visible on the left side of the third paramedic's shirt, as he's doing chest compressions.
Visible crew/equipment: At the start, when Johnny is telling The Stewardess about the underwater rescue and in following shots, the outline of the lavalier mic wire and the dark strap (that holds the transmitter) around Johnny's waist are visible on the back of his shirt, and the mic transmitter is visible on the front, left side of his shirt, above his belt.
Visible crew/equipment: After the airplane rescue, at Rampart when Brackett congratulates Roy and Johnny on a job well done, the outline of the mic transmitter is visible on the front, left side of Roy's shirt, just above his belt.
Visible crew/equipment: When Squad 51 is dispatched to the car on top of a roof, it cuts to John and Roy driving in the squad as John responds to dispatch, and the reflection of the filming vehicle is visible on the squad's surface.
Visible crew/equipment: When Roy leans over Captain Stanley after he was electrocuted, the outline of Roy's mic transmitter is visible on the back of his shirt.
Involvement - S5-E19
Visible crew/equipment: On scene at the accident with the tanker carrying liquid hydrogen, after Chet extinguishes the fire that ignited on Johnny's back, when the fire spreads and the car explodes, the car falls onto its side and the FX stunt platform that the car was resting on becomes visible. Then two shots later that platform has vanished, as they hose down the fire.
Above and Beyond... Nearly - S5-E20
Visible crew/equipment: When Johnny and Roy get back to the station, and Captain Stanley tells them to come into the office where Chief Houts is waiting, the reflection of numerous set lighting can be seen on the squad's chrome spotlight.
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.