Visible crew/equipment: When John and Roy are dispatched to the couple's house, for the second time, after they've checked the rooms upstairs and downstairs they join the couple in the living room, and the reflection of the large overhead set lighting is visible in the mirror hanging over the mantel.
Visible crew/equipment: At the structure fire, when Squad 51 stops at the hydrant to lay the dual lines, as Engine 51 drives past the squad, the reflections of array lighting and the reflector screen are briefly visible. Then when Engine 51 rolls up to the fire, as Captain Stanley tells dispatch to send a second alarm and approach from the west, we can see the reflection of a crew member wearing a long sleeved white shirt and dark slacks, in the window behind Captain Stanley. He's still visible when Squad 51 pulls up alongside Engine 51, and also when Cap tells Engine 9 to lay duals.
Visible crew/equipment: During the structure fire, in the shot after Johnny runs up the ladder to the roof to get to Captain Harmell, a crouching crew member can be seen under the open passenger side door of Engine 17.
Visible crew/equipment: During the rescue of the man trapped in the submerged car, when 110's Captain is handing John and Roy (who are in the water) the cave-in gear's air hose, in the shots from behind him on deck, the reflection of a crew member wearing white pants can be seen on the chrome surface beside him.
Visible crew/equipment: The first three times that Squad 51 is dispatched to 1012 Clinton Drive, before they leave the apparatus bay, we can see the reflections of set lighting in the squad's spotlights, particularly the driver's side.
Visible crew/equipment: At the construction site with the cardiac arrest, the outline of the lavalier mic transmitter is visible on the back, left side of Johnny's shirt, particularly when lifting the man onto the ambulance stretcher.
Visible crew/equipment: After Roy gets chewed out by Dr. Sunderlin, when he and Johnny get back to the station, the spotlight on the passenger side is shiny and reflective, and set lights are reflected in it, then when the dispatcher drops tones for the next run, the spotlight has been sprayed with a dulling spray.
Visible crew/equipment: While en route to the mechanic whose engine fell on him, Mike is driving Engine 51, and seated backwards in the jumpseat behind Mike is Marco, who's wearing a helmet and his turnout, but in the shot from the POV behind Mike, we see the reflection in the rear-view mirror of the grey haired crew member, who is seated facing forward behind Mike.
Visible crew/equipment: At the greenhouse nursery, when Larry is leaning over his uncle, who's lying on the ground, the outline of the mic transmitter is visible on the back of the teenager's sweatshirt.
Visible crew/equipment: When the 15 year old OD is in the ER, after Morton removes the squad's resuscitator from the mask and replaces it with an Ambu bag, the cameraman moves forward and leans in, causing a distinct shadow on Johnny and the patient.
Visible crew/equipment: When Squad 51 is dispatched to a drowning, just as Chet tells Johnny, "Don't go getting yourself damaged," the set lighting is reflected in the squad's spotlights.
Visible crew/equipment: When Johnny walks out of the ER, and finds out from Sally that Roy's been spreading advanced publicity about Johnny's 'modeling career', and then when Dr. Knott joins them, the outline of the mic transmitter is visible on the back of Roy's shirt.
Visible crew/equipment: While en route to the boy who fell in the hole, Mike is driving Engine 51, and seated backwards in the jumpseat behind Mike is Marco, who's wearing a helmet and his turnout, but in the shot from the POV behind Mike, we see the reflection in the rear-view mirror of the grey haired crew member, who is seated facing forward behind Mike.
Visible crew/equipment: When Squad 51 responds to 'man injured', when they arrive at the house, Johnny asks Roy if there's a dog on the roof, and it cuts to a shot of Sheba, the dog, just as she glances toward the tree, and behind the tree we can see the moving legs of a crew member, likely Sheba's trainer.
Visible crew/equipment: After the guys get back to the station following the structure fire, when Roy and John discuss Roy's decision about possibly going to 98's, the lighting equipment is reflected in the driver's side spotlight.
Visible crew/equipment: After the structure fire, when Engine 51 and Squad 51 back up into the apparatus bay, the top of the set at the rear bay door can be seen.
Visible crew/equipment: When Squad 110 pulls up to Chopper 14, the reflection of the reflector screen is visible on the squad's surface, and when all the guys climb into the chopper, the reflector screen's reflection is visible again.
Visible crew/equipment: When Squad 51 is dispatched to the man trapped in the freezer, Johnny and Roy get into the squad, and the reflection of the large set lighting can be seen on the passenger door and vent window.
Visible crew/equipment: After Squad 51 arrives at the scene of the parachutist who's stuck in the tree, when Roy tells dispatch to have an engine respond to their incident, the reflection of array set lighting is visible on the squad's surface.
Visible crew/equipment: When John and Roy are tunneling through to the little girl trapped in the hole, they're in the second larger hole that has been shored up on all sides with wood (to keep it from collapsing), but when Roy points the chrome flashlight down the lateral hole Johnny's digging in, we can see in its reflection that the fourth wall doesn't exist, where the camera and lights are located.
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 ★