Continuity mistake: When Roy and Johnny are with the boy who is trapped on the crane, Johnny buckles the life belt around the boy's waist, and in the following shots the belt's direction flips around to the opposite way repeatedly. Note its stitched leather and tongue buckles.
Cook's Tour - S1-E4
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.
Visible crew/equipment: After they finally get an address for the attempted suicide Squad 51 takes off, and when Engine 51 pulls away from the curb, the shadow of cinematographic equipment is visible on the engine's front, and the reflection of lighting equipment is visible on the side of the engine.
I'll Fix It - S4-E2
Continuity mistake: When Station 51 is at the scene of the oil well eruption, underneath a house which was built atop an abandoned oil field, just after Johnny tells Roy that he thinks the whole foundation is slipping, it cuts to a shot of the front porch as one of the porch columns (and part of another) breaks and falls. However, when the guys finally free the trapped man and carry him out, all the columns are upright once again.
Visible crew/equipment: When Roy and Johnny are trying to get the basketball player (Kareem Abdul-Jabbar) out of the car, and when Roy exits the car to get equipment, the outlines of the mic transmitters and wires are visible on the back, left side of Johnny's shirt, and back, right side of Roy's shirt.
Visible crew/equipment: When Brackett tells the orderlies to take the stock broker to the CCU and they tend to him, an actor's T-mark is visible under the gurney while it's still propped up, just before Dixie stands on that spot.
Visible crew/equipment: After Gage and DeSoto climb the ladder to get the dog off the roof the second time, when it cuts to Rampart there is a man waiting outside the treatment room, and the actor's tape mark is visible on the floor, at his feet.
Visible crew/equipment: After Mr. Howarth confronts his son about the pills his daughter took, when Dixie walks up and tells him that he can see Monica, the actor's tape mark is visible on the floor, at Dixie's feet.
Visible crew/equipment: When Dixie looks for Sally to flush the patient's eyes, she finds her in the hallway, and there are two actors' tape marks on the floor in the waiting room, where Dixie and Mike, the patient's friend, will stand in a moment.
How Green Was My Thumb? - S3-E17
Visible crew/equipment: After Roy and Johnny visit Mrs. Johnson at Rampart, there are three actors' tape marks visible on the floor when they walk past the nurses' station, just before Brackett, Chaplain Miller and Early stand at their marks.
Visible crew/equipment: When Art, The Screenwriter, goes on his first ride-along with Squad 51, just as Art rambles on about the fire truck on its mission of mercy going 80 miles an hour, two shadows of mic/camera equipment are visible on the left and right side of Squad 51's hood. What's amusing is that a moment prior to this, Art actually says that they could mount a camera right on the hood of the truck, when they make the film about paramedics.
Daisy's Pick Blind Date - S4-E7
Visible crew/equipment: When Roy and Johnny are with the hypothermic refrigeration engineer, the outlines of the mic transmitter and wire are visible on the back, left side of Johnny's shirt. Note that when Johnny and Roy are in the ambulance with the patient, Johnny is not wearing the lavalier transmitter and wire anymore.
Visible crew/equipment: When Engine 51 arrives at the toy factory fire and comes to a full stop, we see the hunched over cameraman holding a handheld camera, with another crew member standing right behind him, and just as Captain Stanley opens the door and emerges, we see the cameraman being helped up and both men turning and moving quickly to their left, as Captain Stanley jumps off the engine.
Visible crew/equipment: When Roy and Johnny are working on freeing the man trapped in the vehicle, and then when they are taking his vitals, the outlines of the mic transmitters and wires (running up toward their shoulders) are visible on the back of Roy's and Johnny's shirts. The mic transmitter's outline is also visible on the left side of Christy's sweater, below the waistline.
Visible crew/equipment: During the boating accident rescue, the outlines of the mic transmitters and wires are visible on the backs of both Johnny's and Roy's shirts, on their right sides.
Visible crew/equipment: When DeSoto and Gage are trying to rescue the unconscious boy stuck in the tree, Gage drills a hole in the tree, and when he reaches down to the oxygen tank and then places the tube in the hole, the outlines of both the mic transmitter and wire are visible on Gage's shirt.
Visible crew/equipment: When the babysitter runs into Rampart carrying the boy, both Dixie and Brackett are standing at the nurses' station talking and an actor's white T-mark is visible at Dixie's feet.
Visible crew/equipment: Just as Dixie lets the unconscious teenager's parents walk into the ER treatment room, the actor's T-mark is visible on the floor behind Gage's legs, a moment before Brackett stands at the mark.
Visible crew/equipment: When Early and Brackett try to deal with the elderly group who want to see their friend, as the group walk away toward the waiting room, two actors' T-marks are visible on the floor, one of them is at Dixie's feet, the other beside her.
Cook's Tour - S1-E4
Visible crew/equipment: When Engine 68 pulls into the site with the suicide who has changed his mind, there is an actor's T-mark on the ground behind DeSoto, as he puts on his jacket.
Answer: I believe you are speaking of the old man, Mr. Wilson. He's played by J. Pat O'Malley.
Bishop73
Correct, it was J. Pat O'Malley...he also played the grandfather with his grandson when their rocket exploded, and also played "Old Bill" in the episode with Ann Prentiss, where Gage saves the little girl from the burning tree house, and her mother falls in love with him.