Revealing mistake: In at least three episodes, which include 'Saddled', 'Peace Pipe' and 'Women', the same corner restaurant/hot dog stand (with a striped orange/white awning and green vinyl bar stools) is featured. That would be fine, if it weren't for the fact that in each episode the street it is located on has a different name and different cross streets. It is obviously a set on the Universal Studios lot.
Visible crew/equipment: When Roy has trouble sleeping in the middle of the night, he gets up, and when he goes to the bathroom sink, there is a fully dressed crew member whose reflection is visible in the mirror, as he moves around and looks through the door window towards the actor. Then 51's tones drop, and in the next shot we see that all the other guys of Station 51 have been lying in their beds, before getting up and putting on their turnouts.
Continuity mistake: Having trouble sleeping, Roy gets up in the middle of the night at the station, and when he puts on his turnout trousers his right suspender becomes unfastened at the front, and hangs down the back of his leg when he walks into the bathroom. However, in the next shot as he enters the bathroom the suspender is properly fastened.
Continuity mistake: After 51's guys rescue the man from under the fallen engine, when the ambulance leaves we can see only the name Mayfair is printed on its side, but en route to Rampart and when Roy has the ambulance stop and then go, there's a red cross printed on the surface above Mayfair.
Continuity mistake: During the structure fire, after the parents realize their son ran back into the burning house to get the dog, when the father tries to go after the boy we can see the man's wearing a striped T-shirt under his robe, but when Roy rescues both the boy and the dog, the father is now wearing a white T-shirt under the robe.
Other mistake: After rescuing the boy and his dog from the structure fire, when both of 51's rigs are backing up the driveway, the office door opens and we can see through the glass door that someone is standing there, even though they're all on the rigs. Next shot, that phantom individual has vanished.
Visible crew/equipment: During the structure fire, after Roy finds the boy and his dog under the bed, when Roy heads down the stairs and then rushes back up, as he gets to the top of the stairs when the camera pans to the left we can see the barndoor set lighting, at the top left side of the screen.
Other mistake: When Station 51 is dispatched to the structure fire in the middle of the night, once they arrive at the burning house, one of the first shots shows a crowd of bystanders, many in their robes. That footage is from season 1, the pilot episode "The Wedsworth-Townsend Act", during the factory fire at the start of that episode.
Continuity mistake: Dispatched to the structure fire in the middle of the night are Station 51, Engine 95, Engine 105, and Truck 107, but on scene we see Engine 800, Engine 801, and also Engine 10, which is all footage from the first season's pilot episode "The Wedsworth-Townsend Act."
Visible crew/equipment: After Roy gets chewed out by Dr. Sunderlin, when he and Johnny get back to the station, the spotlight on the passenger side is shiny and reflective, and set lights are reflected in it, then when the dispatcher drops tones for the next run, the spotlight has been sprayed with a dulling spray.
Visible crew/equipment: While en route to the mechanic whose engine fell on him, Mike is driving Engine 51, and seated backwards in the jumpseat behind Mike is Marco, who's wearing a helmet and his turnout, but in the shot from the POV behind Mike, we see the reflection in the rear-view mirror of the grey haired crew member, who is seated facing forward behind Mike.