Revealing mistake: At the apartment complex fire, after Johnny is knocked unconscious by the explosion, when the Pasadena fireman finds him and has to lift him up, it's funny how even though Johnny's unconscious we can see that he actually helps to stand himself up, so the fireman can lift him up and carry him out.
Visible crew/equipment: Just after Herbert leaves the station in the morning, dispatch sounds the alarms, and when Roy and John are in the squad while the dispatcher begins talking, there are nice reflections of the camera, reflector screen (in the background), and crew members/cameraman who move around, that are visible on the surface of the spotlight. Additionally, the shadow of the boom/mic is perfectly visible on the windshield as it moves down.
Visible crew/equipment: At the apartment complex fire, after Roy removes the ladder from Engine 51, the Pasadena engine rolls up, and when the Pasadena Captain walks toward Captain Stanley, the second cameraman wearing a brown blazer can be seen standing on the very top of Engine 51 to the left, shooting the overhead footage of the Pasadena engine that was just shown.
Visible crew/equipment: At the apartment complex fire, when Truck 82 raises its ladder, we can see the second floor balcony behind the rig, and there is a crew member wearing a long sleeved blue shirt and white hat, standing in front of the corner apartment, where there should be smoke pouring out, but there is none. The reflection of the cameraman/crew member wearing a white hat also becomes visible in Truck 82's wing mirror.
Continuity mistake: During the fire at the apartment complex, when John and Roy go into the apartment to rescue the woman, they throw a coat over her, but then the explosion occurs knocking John and the woman unconscious. When Roy puts her over his shoulder and starts walking out the coat is not over her, but when he gets to the balcony she's covered by the coat, yet when the Pasadena fireman goes back for John, that coat is still lying on the floor.
Revealing mistake: After Station 51 is dispatched to the 'plane crash into a structure', when Engine 51 pulls over to lay the dual lines at the hydrant, we can see up the block on the left, the back side of the apartment complex where they are headed, and most of the back windows are boarded up. The following scene takes place at the front doors of those apartments, where people supposedly live. The show used some real locations (not just Universal's sets) where there had been real fires, to film carefully controlled fire scenes.
Continuity mistake: When the guys decide to eat lunch before resuming CPR practice, Chet puts the CPR mannequin upright beside the fridge. Chet's wearing his regular black shoes, and the CPR mannequin is wearing white sneakers. However, in the close-up of The Mouse crawling under the fridge, the leg we see near The Mouse is wearing a brown rubber firefighter's boot.
Other mistake: After Early carries Martha into treatment 3, and he and Brackett begin examining her, there's a nice exterior shot of what is supposed to be Rampart, only it's not actually Rampart, and we know this since throughout the show's run there are numerous exterior shots of Rampart from every angle.
Revealing mistake: During the fire at the apartment complex, there are strips of black material nailed to the tops of windows where the FX fire shoots out from below, and the doorway Roy passes when he's pulling on the hose has a fake ceiling and wall nailed directly into the door jamb, to control the strip of FX fire at the side.
Revealing mistake: At the apartment complex fire, just as Chet climbs the ladder and Marco holds the top of the ladder on the second floor balcony, we see the plumes of FX smoke spurting from the side inside the doorway behind them, and even see something quickly fanning the smoke.
Other mistake: At 6:50 AM, just before the dispatcher transmits the testing tones to Station 51 which wakes everyone up, we're shown the exterior shot of the station and the two flags are already flying. Guys of C shift (as Chet states) haven't arrived yet that morning, so they didn't raise the flags, and we know it's Mike who always raises the flags on A shift, but he only just woke up when the dispatcher sent the tones.
Continuity mistake: When Roy and Johnny get back to the station, Johnny asks Chet about the condition of the house after the fire, and in the wide shot Johnny has a really red pimple near his chin, but in his closeup the pimple has vanished, only to reappear in the next shot.
Continuity mistake: After Chet sees The Mouse run under the fridge, when the guys are discussing The Mouse Johnny's medical holster is clipped at his right hip, but when they're dispatched to 'man unconscious at laundromat' his medical holster is now at his left hip as he walks to the squad.