Visible crew/equipment: At the start, when Squad 51 rolls up on the car accident scene, in the shot from inside the squad we can see the entire area around the wrecked car, and there's only a utility pole, short wood fencing, and trees. When Roy and John are treating Paula, and then removing her from the car, in the overhead shots as the camera faces the wrecked car and 51's rigs, there's a very large rectangular shadow being cast over the car, which is presumably from a reflector screen facing the front of the car.
Visible crew/equipment: After Squad 51 is dispatched to the cliff rescue, when Roy and Johnny board Copter 10 at Rampart, the reflection of the production vehicle/equipment is visible on the glass surface at the helicopter's nose.
Visible crew/equipment: In the treatment room, when Brackett gives the diabetic man an insulin shot, there is an actor's tape mark on floor at Dixie's feet, that we can see under the gurney.
Visible crew/equipment: When Early and Dixie are in the treatment room with Jenny, after Early asks Jenny if she can move her legs, the moving shadow of the boom and mic are visible on the wall behind Dixie.
Visible crew/equipment: At the scene of Paula's traffic accident, when Captain Hammer stands in Engine 51's cab and tells Marco to get the reel line, the reflection of equipment and set lighting are visible in the chrome surface of driver's side spotlight.
Visible crew/equipment: During the rescue at the construction accident, when the man with the back injury is hanging from his line and is lowered after Roy untangles the block, we can see that in addition to the rope wrapped around the man there's wire and support that go under the man's jumpsuit. The wire/support are gone once he's lying on the balcony and they remove the rope.
Visible crew/equipment: Station 51 responds to a building collapse with the trapped boy, and when they enter the building with Tommy's friend, the actor's white T-mark is visible on the floor.
Visible crew/equipment: At Rampart, when Gage and DeSoto walk into the staff lounge, where Dixie and Dr. Brackett are seated at the table, there is an actor's T-mark on the floor behind Dixie, where DeSoto stands.
Visible crew/equipment: On site at the construction accident with the back injury victim, when Roy climbs over the tower's railing we can see the yellow canvas strap attached through the leather loop of his lifebelt, but when he descends to the injured victim, the yellow canvas strap is now also attached to a carabiner protruding from under his turnout coat, by his pants, which presumably is attached to additional hidden support.
Visible crew/equipment: On site at the construction accident, when the man with the back injury is lying in the stokes and being lowered with the ladder, a crew member/cameraman is visible on the landing at the lower right side of the screen.
Cook's Tour - S1-E4
Visible crew/equipment: At the construction site, when Johnny and Roy climb the tower mast, they stop on the blue platform with the crane operator's cab before continuing up to the main jib. When Roy, Johnny, and the man they rescue walk back across the jib the man slips, and there are a few shots showing the underside of the blue platform, and we can see people moving around on that platform overhead. There should only be four people on the tower crane: Roy, Johnny, the man they rescue, and the officer holding the bullhorn, who's standing at the other end of the jib, by the mast. Nobody is supposed to be on that platform.
Cook's Tour - S1-E4
Visible crew/equipment: At the construction site, when Roy and Johnny walk across the tower crane's main jib, there's a shot of the entire top of the crane, and we can see the cameraman at the tower peak, who is shooting the footage of the stunt guys from the overhead angle. He wasn't in the previous long shot of the crane. This does not refer to the officer who is standing on the main jib.
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.
Cook's Tour - S1-E4
Visible crew/equipment: When Engine 51 returns, after Gage and DeSoto have finished their beef bourguignon, as they walk into the kitchen the actors' black marks are visible on the floor, where they are about to stand.
Cook's Tour - S1-E4
Visible crew/equipment: When Jay walks into the ER treatment room, where his unconscious brother has possible brain damage, two white marks are visible on the floor, behind Dixie, and another couple of marks will become visible as this scene continues.
Cook's Tour - S1-E4
Visible crew/equipment: At Rampart, after the baby's birth, when Gage and DeSoto walk over to Dixie, the first actor's T-mark is visible on the floor just before Gage stands there, and a second actor's mark is visible under the stool, where DeSoto will be seated in a moment.
Cook's Tour - S1-E4
Visible crew/equipment: After Roy and John pull up to the house with the woman in labor, when the deputy pulls up behind Squad 51, the reflection of production equipment alongside the lamppost is visible on the car's surface. In the previous long shot of the house, we see there is only a large area of grass in front of the house.
Visible crew/equipment: At Rampart, when Brackett walks over to Roy to speak with him about the birth of another baby, the actor's black tape mark is visible on the floor, just before Brackett stands there.
Visible crew/equipment: When Johnny and Roy are back at the command post and hand over the looter (Tony Dow) to the deputy, the four actors' marks are visible on the ground where they stand.
Visible crew/equipment: After Roy helps the looter into the squad, when Johnny goes to the motorcycle and finds the leather bag full of jewelry, the mic wires that run from under his shirt/belt into his right pants pocket (with the transmitter bulge) are visible as he bends down.
Answer: I was rewatching a few first season episodes of Charlie's Angels (1976), and in S1xE6 "The Killing Kind," I recognized the same actor. So, to finally fully answer your question, the two baseball players in School Days are played by Rod Perry and Sean Fallon Walsh.
Super Grover ★