Revealing mistake: After the MI patient from the construction site is brought to treatment 1, when Early uses the laryngoscope for an endotracheal intubation, we can see that he merely places the laryngoscope at the side of the man's face, especially since we can still see the entire distal end beside the man's neck.
Deliberate mistake: After Johnny's and Captain Stone's efforts, when the construction site's cardiac arrest is wheeled into Rampart, the problem is twofold; First, we hear Roy's voice saying, "Full arrest, number four," even though Roy is not actually on this run (that line is from S4xE21 "Back-Up", when they wheel the cardiac arrest into treatment 1, after defibbing him atop Engine 51). And second, the attendant pulling the stretcher changes, and the EKG monitor lying on the patient is the old blue Datascope 850 from earlier seasons (this shot is from S4xE7 "Daisy's Pick", the hypothermic victim - note his wrapped foot!), whereas at the construction site and when he's wheeled into the treatment room, the EKG monitor is the newer white Datascope M/D2.
Other mistake: At the construction site, after Johnny administers the epinephrine to the cardiac arrest, 39's paramedic resumes CPR, and when they're lifting the patient onto the stretcher Johnny says, "Stop CPR," but the subtitles read, "Start CPR," which makes no sense since they've been doing CPR all along.
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.
Character mistake: At the construction site, while the paramedics are defibbing the cardiac arrest Stoney's on the line with Rampart, and Brackett orders, "Administer 5ccs 1 to 10,000 epinephrine IV," to which Stoney responds, "Administer 5ccs epinephrine, 10-4, LA," even though he's speaking to Rampart not to LA dispatch.
Continuity mistake: During this episode Brackett is wearing a tie with white, light blue, and dark blue broad stripes, which should be tied in an identical manner in consecutive shots, but it's not. One example is when Brackett examines the tree surgeon, but when he waits in the hall with Morton and Dixie while Malcolm takes x-rays, Brackett's tie is tied differently, and when he walks back into the room the tie reverts back.
Continuity mistake: After Roy finds Willy, when he calls Captain Stanley to help get Willy out, Roy's on Willy's left and Captain Stanley's on his right as they rush out, but in the next shot they've switched, Captain Stanley is now on Willy's left and Roy's on his right, just before the explosion.
Continuity mistake: During the warehouse fire, Johnny removes his turnout when Captain Stanley calls for the ambulance, then when the ambulance arrives John's wearing the turnout and one burn victim has the sheet over him, but then the turnout and sheet vanish, and as the ambulance attendants bring the stretcher, Johnny places the sheet on the victim, and in the overhead shot as Cap is told about Willy, Johnny's wearing his turnout again. The Biophone also keeps jumping from being beside Squad 51 to being between the victims.
Deliberate mistake: After the fireworks begin exploding at the warehouse fire, when Captain Stanley and Roy are helping Willy out, they are knocked to the ground by an explosion, and in two of the following exterior shots the large sign that reads "Kiddytime Toy Co" is visible. This shot is from season 4, episode "The Screenwriter", when the guys respond to the fire at the toy factory that also made fireworks.