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.
Continuity mistake: When the boy who fell over the cliff is brought into the ER, Dix tells them to bring him to treatment 3 and we see them at treatment 3's door, which is on the same side of the hallway as treatment 4, with the red line closest to it (hall has red, green and yellow lines on the floor which run the length of the hall) However, in the shot from inside the treatment room, they're not in treatment 3, but are actually in treatment 1. Note that we see treatment 4 directly across the hall, which means they're in treatment 1, and also see the yellow line is closest to the door which means it's on the opposite side of the hallway.
Continuity mistake: When the guy who was injured in the manhole is brought into the ER, Dix tells them to bring him to treatment 6 (which is around the corner from the other treatment rooms, and has no color lines that run past its door), then we see him wheeled into treatment 6 in the shot from the hallway. However, in the next shot from inside the treatment room we can see they're not in treatment 6, but actually in treatment 1, note the red, green, and yellow lines on the hallway floor in front of its doorway, and treatment 6 has no color lines that run past its doorway.
Revealing mistake: When Station 51 responds to the traffic accident, after Captain Stanley hands Johnny the Ajax tool, in the closeup it's obvious that the hands are not really Johnny's. Then there's another shot of the real Johnny, but once he removes his goggles, interestingly it's the stunt double who's in the following shots by the car, even when Johnny cuts himself, it's the stunt double.
Character mistake: When Johnny and Roy are in the kitchen and start reminiscing about when they first met, Johnny recalls those days and says "I was working B shift at Station 8's," however, Johnny was actually working at Station 10.
Deliberate mistake: When Roy and Johnny are on the Coast Guard helicopter, approaching Catalina Island with the injured diver, there is a closeup shot of them looking out the windows, which is a flipped shot - note the backwards paramedic patch on the right sleeve, instead of being on the left sleeve.
Other mistake: After Station 51 arrives at the structure fire, Captain Stanley tells Mike to get water to their lines (charging the two lines) and then mule the supply line back to the hydrant. When Marco and Chet get the two lines, they head to the house with Captain Stanley and start hosing the fire down with charged lines. A few shots later, we see Mike going to the back of Engine 51, and the two lines that Chet, Marco, and Cap have been using are flat and not even charged yet.
Other mistake: The dispatcher gives the address of "woman trapped on a wire" as "Commercial Studios,1122 Dellini Plaza", and as Engine 51 drives past the front gates, the large sign reads "World Pictures Corp." Additionally, the address of World Pictures Corp is 1731 Carlson, when we see the same footage of Engine 51 driving past the sign in episode "The Exam" in season 6.
Continuity mistake: When the TV catches fire in the kitchen, Captain Stanley unplugs it, and when it cuts to Roy running into the kitchen with the fire extinguisher, he passes Marco, who just ran into the apparatus bay. All of this while we hear Cap's voice telling Marco, who already ran out, to get the asbestos blanket. Then, in the next shot, Marco is still standing behind Captain Stanley in the kitchen.
Other mistake: Twice during this episode, when they're dispatched to a "woman trapped on a wire" and also to the "train fire", we see Engine 51 heading out with two firemen standing at the back of the engine, and they are Johnny and Roy. This footage is actually from the episode "The Old Engine" in season 3, when they got the new Ward La France engine for Station 51, and since Roy and Johnny were waiting for the previous shift to return with the squad, Captain Stanley told them to jump on the back and go with them on their first run with the new engine.
Continuity mistake: When Roy and Johnny are in the backyard with the couple and the mother-in-law, after Johnny gets off the phone with Brackett, he has the black notebook in his left hand, but in the side shot it's in his right hand, then it returns to Johnny's left hand.
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.