Revealing mistake: After Station 51 is dispatched to "traffic accident with injuries," when they're on scene at the plant with the injured tanker driver, pay particular attention to the background behind Engine 51 while Roy is on the Biophone with Rampart. When Brackett says, "51, can you give me any more information," we can actually see Station 51 aka 127, directly behind Roy.
Revealing mistake: When Squad 51 is dispatched to the man who has difficulty breathing, once they arrive and it cuts to a closeup, at the top of the screen there is a small dark film square that moves towards the left corner, and then it stays there in the following shots facing Johnny, until he contacts Rampart on the Biophone.
Revealing mistake: After Squad 51 is dispatched to the 'electrocution in a house', while Johnny goes to the garage to turn off the power, Roy waits at the doorway to go inside to the victim. In this interior shot facing the doorway, we see what is supposed to be the brick chimney at the side of the house next door, and the top of that set is visible. Plus the fact that this chimney is not nearly as deep as the one they passed by in the exterior shot.
Revealing mistake: When Gage and DeSoto are on scene with the unconscious woman and a dog, they break the front window of the house. In the interior shot as DeSoto climbs through the window, there is a white wall beside the window outside, which blocks the view of the "outside." That wall does not exist in the exterior shots. The same thing happens when Gage opens the front door.
Revealing mistake: At the end of the 'crashed plane in a tree' rescue, Tom falls upside down in front of Roy and John, who are standing on branches way high up in the tree. Then just as the scene ends and the screen fades out, we can still see Gary Crosby (Tom) having fun jumping hard up and down on that "tree branch" that he's now also standing on, and Randy Mantooth starts cracking up.
Revealing mistake: When Roy and Johnny are in the radioactive lab, loading the unconscious doctor with severe radioactive poisoning onto the stretcher, note that the unconscious doctor is lifting his own left arm, and moving it onto the stretcher so it's resting beside him properly.
Revealing mistake: On scene with the little girl trapped in the hole, when they shine the flashlight down the hole in the overhead closeup, it's too obvious that it's a doll with its arm raised up, plus the fact that we see plenty of space around the doll, contradicting the plot of the little girl being wedged in a tight space.
Revealing mistake: When the boy is discharged from the ER and is reunited with his dog, John and Roy are standing near the squad watching the reunion, and the usually highly reflective surface of the passenger side spotlight has been sprayed with a dulling spray, to temporarily dull the surface.
Revealing mistake: After Squad 51 is dispatched to the motorcycle accident, there are wide shots of the squad driving through the hills, then in the closeups of Roy and John, the squad shakes from side to side to mimic driving, but we can see that the surrounding rocky area behind the squad (matte painting) does not actually change at all.