Continuity mistake: When Dixie shows Johnny the newspaper, Johnny reads the ad aloud which states, "Wanted, 1925 Paige fire truck, $25,000, if in mint condition," and Johnny says that it is exactly what the ad submitter wants. The "it" being Roy and Johnny's refurbished fire truck. The problem is that in 3x2, "The Old Engine," when Johnny and Roy are telling Chet and Marco about their purchase, Johnny says that it's a 1932 Dennis, and when they're looking it over, the blue "Dennis" emblem is attached to the hood of the engine.
Continuity mistake: When they pull the man with chest pains from the pickup truck, Dixie says treatment 3, which is opposite the receiving entrance and on the same side of the hall as the nurses' station, closest to the red line on the hallway floor, but when Dixie leaves the treatment room it's at the side of the hallway closest to the yellow line, and since there's a window on its door we know it's actually treatment 1 that he's in, not 3.
Continuity mistake: When Johnny and Roy are at the apartment building with the broken elevator, Roy's watch is gone when they climb the steps, but he's wearing the watch when they enter the apartment, then it vanishes when they head back down. That watch reappears again, disappears and reappears until they go back up to the apartment for the second time.
Continuity mistake: At the nurses' station, after Roy tells Brice that Brightweiser will be okay the two of them walk to receiving carrying their gear, with Roy holding the Biophone and defibrillator, but as they head through the doors both the Biophone and defibrillator have each turned around in Roy's hands, and now face the opposite way.
Continuity mistake: Squad 51's lightbar has a center chrome piece which has slats at the front and is solid at the back. When the squad's dispatched to the vehicle accident with the two student drivers, on scene the lightbar's chrome center is on backwards, it's solid at the front for some inexplicable reason.
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.
Continuity mistake: When the unconscious boy is brought to the ER, he's taken into treatment 2, with a windowless door, but when Early is doing the lumbar tap on the boy, the door behind Early has a window, and also by the way the room is set up, we know it's treatment 1 he's in, not 2.
Continuity mistake: At the restaurant, when they begin to work on getting Mrs. Merkle out from under the car, Vince sets the Biophone down on the table, and there's a netted, red glass candle on the table, but in a following closeup the candle's net has vanished and it's pinkish clear glass now. Other items on the table change as well.
Continuity mistake: When Ruthie is wheeled into the ER, Dixie tells the attendants to put her in the treatment room where Dr. Early's waiting, and they wheel her into treatment 2 which has a windowless door, but when they're in the room the door has a window, which means she's in treatment 1, not 2. Plus the fact that both treatment rooms are set up differently.
Continuity mistake: In the opening shot of Roy and Johnny at the whale tank, the maintenance guy behind them is standing between the red bleacher seats and purple seats below, but in Roy and Johnny's closeups the guy is standing between the two top purple bleacher seats, then when the whale splashes, it goes back and forth yet again.
Continuity mistake: When the patient with the heart wound is brought to the ER, he's wheeled into treatment 2, which has a window on its door, and is on the side of the hallway with the yellow line closest to it. Later we see treatment 1 twice, when Vince brings in the burglary suspect with a bullet in his leg, and also when John and Roy rush the baby to the ER. They used the same room as treatment 1 and treatment 2, but there are just two treatment rooms on that side of the hallway and only one of them has a window on its door - the one that's opposite the nurses' station, treatment 1.
Continuity mistake: When Squad 51 arrives at the training center, Johnny's turnout coat is open and we see that he's only wearing an undershirt, but when it's 18's turn at the sulfur trioxide, as Johnny's putting on his air mask he's wearing the blue uniform shirt under his turnout.