Continuity mistake: When Squad 51 is dispatched to the possible heart attack, the address given is 11044 Conquistador, but when they arrive at the incident the addresses on the homes are 8042 and 8046.
Continuity mistake: During the house fire, Marco's holding the hose behind Chet, while Chet is kicking open the front door just before it flashes, but in the next shot both Chet and Marco are manning the hose when the fire flashes, knocking them down the stairs.
Continuity mistake: Marco's mustache goes missing when Station 51 is dispatched to the structure fire, but then it reappears.
Continuity mistake: During the actual rescue at Catalina Island, Johnny and Roy are now wearing water-type shoes, not their uniform shoes.
Continuity mistake: After bringing the man who choked on a beer can's pull tab to Rampart, when Squad 51 returns to the station and backs up the driveway, the engine seen parked in the apparatus bay is the Crown from seasons 1 and 2, not their current Ward LaFrance engine.
Smoke Eater - S4-E16
Continuity mistake: When Billy's mother waits in the hallway while Early examines Billy, the window behind her is on the same side as the ER's receiving entrance. Note that outside the window there's a blue metal shade at the top, which does not exist in any exterior shots of that side of the ER.
Transition - S4-E15
Continuity mistake: When Gil is assigned to ride along with Squad 51, en route to the incidents there are only two people seated in the squad in the shots shown.
Captain Hook - S6-E8
Continuity mistake: During the police helicopter rescue, Roy's, Johnny's, Marco's, and Chet's shoes change to water-type shoes once they rappel down the cliff, and deal with the rescue.
Continuity mistake: After Dixie has the talk with Molly about using 51 as a crutch, it cuts to the shots at the movie studio with stunt drivers being chased, and the passenger who has his head out the car window is bareheaded, but in the closeup he's suddenly wearing a knit cap on his head.
Continuity mistake: While Johnny tries to reach the man who fell over the cliff, when the bicycle falls to the bottom of the canyon both tires break free from the frame, but when the officer retrieves the bicycle, only one of the tires is off, the other is undamaged and on the frame.
Continuity mistake: When John and Roy walk into the house with the pregnant gunshot victim, only John's wearing a helmet and he places it on the floor near the victim's husband, but in all of John's closeups (from the unusual POV looking up at him) his helmet is on the counter. Additionally, there are blue glasses upside-down on the side of the dish drainer, but in those closeups of John the glasses have vanished, and the glasses vanish again when Roy helps the husband get on his feet. Also notice that there's now a blue glass in the sink.
Continuity mistake: There are only two ambulance attendants who take the pregnant gunshot victim to the vehicle, but en route we see two attendants in the front seat - driver and passenger, and a third attendant is in the back with John and the victim. Then when they reach Rampart, the attendant that was in the back with John has vanished and he's the one who opens the back door from the outside. As an aside, in the ambulance, when John talks to Rampart about fetal heart tones, we see the attendant is actually mucking around with the IV drip.
Daisy's Pick Blind Date - S4-E7
Continuity mistake: When John shows Chet the card with the address that Daisy gave him, Chet quickly takes John's pen to write the address, and when John grabs his pen back he quickly and unsuccessfully tries to put the pen back in his shirt pocket, but in the next shot the pen's in his pocket.
Daisy's Pick Blind Date - S4-E7
Continuity mistake: When John and Roy are with the little boy in respiratory arrest, while John uses the Ambu bag his watch reads 12:15, then he informs Rampart that they have O2 on the boy and goes back to the Ambu bag, and now his watch reads 12:25, though it's only been a minute.
Continuity mistake: When Station 51 is dispatched to 'vehicle accident with injuries', Roy is in the locker room still getting into his uniform with his shirt untucked and belt undone when re runs into the apparatus bay, but in the next overhead shot Roy's uniform is on properly.
Continuity mistake: When Chet and John are by the sink talking about Chet's appearance on the news, in the reflection we can see the three lockers behind Chet, and in the next shot the door of the fourth locker is wide open, blocking the third locker, and we can see that it's open because of the poster that's taped to the inside of the fourth locker's door.
Continuity mistake: After loading the officer with the gunshot wound onto the ambulance, en route to Rampart when Johnny is checking the wound, Johnny's watch reads 11:10, but when he's adjusting the mask and the resuscitator regulator, his watch reads 11:55.
Continuity mistake: After the sniper throws the rifle out the window, Captain Stanley gives the orders over the HT to Engine 12, Truck 23 and Engine 23, and the next few shots of the rigs are from previous episodes including 3x7, "Promotion", when Roy and John rescue the security guard at the structure fire.
Continuity mistake: When John is in the lion's pit with the injured photographer, as he's loading her into the stokes his watch reads 3:40, but after they lift the stokes, when he's on the Biophone with Rampart his watch reads 12:15.
Continuity mistake: Before Mr. Laurents walks into the station with the bag of money, Roy's holding the coffee pot with his right hand, then it's in his left hand, between shots.
Answer: It is standard practice to wet down driveways so that they stand out in a long shot.
stiiggy