Continuity mistake: After bringing Old Bill to the ER, when Squad 51 gets back to the station, in the shot of the squad driving backwards toward the driveway, the engine we see parked in the apparatus bay is the Crown from the first two seasons, not their current Ward LaFrance.
Continuity mistake: When Station 51 is dispatched to 'man down', Cindy and her mother are standing in front of the rear bay door, but they vanish in the next shot as the guys get ready to leave.
Visible crew/equipment: After Station 51 responds to the unknown type rescue, Engine 51 leaves on another run, but when Johnny and Roy go into the house with the wife of the man who lost his voice temporarily due to the dieffenbachia plant, the bulging outline of the lavalier mic transmitter and wire are visible on the back of her white robe.
Visible crew/equipment: After Station 51 is dispatched to the bulldozer accident, just before Engine 51 comes to a stop at the junkyard there's a shot from the perspective of Engine 51's roof, with the Beacon Ray dome light in front, and on the light's red and chrome surface we can see the reflection of the camera mounted on the roof behind the dome light.
Visible crew/equipment: After the boy who ingested the ant poison is loaded onto the ambulance, when the back doors are shut, the reflection of the location set lighting is visible in the ambulance window and on its surface.
Visible crew/equipment: After Johnny carries Cindy down from the treehouse, when Cindy's mother joins them, the bulging outline of the lavalier mic transmitter is visible on the back of her white sweater.
Visible crew/equipment: When Roy and Johnny get to the gas station, Captain Stanley tells them to look at the owner of the station, and when the owner leans over and places the nozzle back on the pump, the outlines of the mic transmitter and wire are visible on the back of his shirt.
Visible crew/equipment: When Squad 51 is dispatched to 'person caught in a mailbox', have a look at the squad's license plates when it rolls up on scene. The plates read "70324H" which is the California commercial plate number for Squad 51, not the usual prop dept's license plate "E999007." It was the prop dept's responsibility to change from the commercial plate to the prop plate, but this scene slipped by them. It's also interesting to notice that this scene takes place at a real intersection up the block from Universal Studios, which is the direction Squad 51 came from. Note the "Black Tower/MCA Tower" in the background, which houses Universal's executive offices.
Visible crew/equipment: After Station 51 is dispatched to the fire at the refinery, when they reach the refinery and make a right turn the view is from atop Squad 51's roof, and the reflection of the covered camera and part of the cameraman's head are visible in the squad's lightbar.
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).
Visible crew/equipment: When Squad 51 is dispatched to the "possible heart attack," just as the squad rolls up on scene, we can see its real license plate with number 70324H, instead of the prop plate number E999007.
Other mistake: When Squad 51 is dispatched to "possible heart attack" the address is "91st and Formosa" (the 'Black Tower' can be see behind the Chevron sign when the squad rolls up), and later when they're dispatched to "person caught in mailbox" the address is "Beverly Blvd and Main." What's funny is that the two incident scenes are filmed at the same corner of the intersection, with Universal's 'Black Tower' nearby. Have a look.
Other mistake: When Roy and Johnny are working on the squad's engine, while Johnny's lying on the mechanic's creeper, Roy is holding a spray can with white tape wrapped around the top of the can, so the brand name would not be visible.
Continuity mistake: When Chet is being timed while putting on his gear, Squad 51 is parked much further up than the engine, providing more room in the apparatus bay behind the squad to run the drill. Then when Station 51 is dispatched to the explosion, the squad's parked normally. Additionally, we see the front bay door is closed, but that's impossible considering how far up Squad 51 was parked during the drill.
Revealing mistake: When Station 51 is dispatched to the chimney explosion, en route there is 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 chopper flying overhead.
Continuity mistake: When Roy and John are in the ER's staff lounge discussing Donaldson, Roy's button, second from the top, is buttoned up in the wide shots, but is unbuttoned in his closeups during the conversation.
Continuity mistake: When Roy and Johnny are with the man in full arrest on the tower at the refinery, Johnny hooks up the Datascope with the wire, but in all the overhead shots there is no wire at the back of the Datascope monitor.
Continuity mistake: At the refinery fire, when Johnny and Roy are on the tower with the collapsed worker, Roy throws the line down to Truck 127's Snorkel for their gear, and as Roy pulls it up, the gear is tied up quite differently depending on the angle of the shot.
Continuity mistake: When Kent (Bobby Sherman) is ready to leave Station 51, the guys are about to sit down to dinner and the table is full of food, plates, cups, utensils, etc, but when the tones drop for the refinery fire and everyone rushes into the apparatus bay, the table is seen behind them and it's bare. Also, the order in which the guys run out of the kitchen is completely different, depending on the angle of the shot.
How Green Was My Thumb? - S3-E17
Other mistake: When Johnny and Roy take the elevator with the nurse, they take the elevator near the nurses' station, at the south end of the ER wing, and Johnny follows the nurse onto the 4th floor to try and get her name. This is completely impossible considering the actual floor plan of the hospital, since in all of the exterior shots of the ER it's only 2 storeys.
Answer: It is standard practice to wet down driveways so that they stand out in a long shot.
stiiggy