Revealing mistake: After Johnny's line gets snarled while testing Wally's equipment at the studio, when Roy lowers himself on his own line wearing his lifebelt, we can see the added carabiners that are attached to the lifebelt which go down into Roy's pants, and are presumably attached to the extra support the actor is wearing under his pants.
Visible crew/equipment: At the refinery fire, after Roy gets into the ambulance with the patient Johnny shuts the back doors, and when the ambulance backs up the reflection of a crew member with paperwork (script?) is visible in the left ambulance window.
Revealing mistake: At the studio, in the overhead shot just as the squad is about to reach the building where Johnny will be testing Wally's equipment, the 'Black Tower', which houses Universal's executive offices, is visible in the background, and then in the roof shots when each of the guys repels down individually, the Sheraton-Universal is visible in the background.
Visible crew/equipment: When Roy and Johnny are with Johnny's friend, the stunt coordinator, trying out the new gear, the outlines of their mic transmitters are visible on the left sides of Johnny's and Roy's shirts, above the belts.
Audio problem: After the rescue at the refinery fire, while they load the ambulance, when Roy and John are being thanked the man's mouth movements are not in sync with what we hear.
Continuity mistake: When Station 51 is dispatched to the 'unconscious female in a car' it's 8:20, but when Roy is on the Biophone with Rampart his watch reads 11:05, and John's watch reads 12:30 as he's checking the woman.
Continuity mistake: On the roof at the studio, Wally sets up John's gear and anchors his rappelling line onto a single carabiner which is attached directly to the belt support around John's waist. Yet when Johnny flips upside down while rappelling down, in the closeups when Roy joins him, that carabiner is now locked off onto another carabiner, which is attached to John's belt, and both of their locking mechanisms are red. Then when John's on the ground, the carabiner attached to his belt and anchor is entirely silver.
Continuity mistake: When Roy and John are at the studio so John can test out Wally's rappelling gear, on the roof John's wearing his medical holster, but Roy is not, but when each rappel down in the wide shots they're both wearing it. Then in their closeups while hanging on their lines, Roy's wearing his medical holster, but Johnny's has vanished, then on the ground Johnny's wearing his and Roy's has vanished.
Continuity mistake: At the studio, when Roy and Johnny are on the roof with Wally to test out Wally's rappelling gear, before Johnny rappels down the thin swami around Johnny's waist and the loop at the back are both green, but once he rappels down the swami belt is grey and the loop is blue.
Visible crew/equipment: When Johnny and Roy are with the man whose fingers are caught in the chain of the garage door opener, just as the man's wife sticks her head out the door to direct 86 to the garage, the outline of the mic transmitter is visible on the back of her blouse.
Visible crew/equipment: At the studio, before John tests Wally's equipment, when Roy says that he's going to get their equipment from the squad, Johnny rushes after him and we see the reflection of the camera crane and array lighting facing Squad 51.
Continuity mistake: When John and Roy rappel down together after John's rope kinked up, as they reach the bottom Roy and John remove their helmets, but as Wally rappels down both paramedics still have their helmets on in the overhead shot.
Visible crew/equipment: When Chet tells Roy that Captain Stanley wants to see him in the office, a tape mark is visible on the floor in front of Cap, just as he tells Roy not to tell the other guys, and then when Roy asks what happened.
Visible crew/equipment: After Roy and John get back to the station, Chet informs Roy that Captain Stanley wants to talk to him, and when Roy's in the office the actor's tape mark is visible on the floor, as Cap tells him not to tell the other guys and when Roy asks what happened.
Visible crew/equipment: After their shift is over, all the guys wait in the apparatus bay for Captain Stanley to come out, and when Medford walks over to them, an actor's tape mark beside Chet's foot and another near Marco's foot are visible on the floor. Then when Cap walks out, another tape mark is visible on the floor in front of Mike's foot.
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 ★