Continuity mistake: When Johnny is writing the 'for sale' sign about his Land Rover, in the wide shot the two phone numbers begin with "853" and "352", but in the closeup a piece of paper has been glued over the phone numbers, and the new numbers now begin with "321" and "749."
Visible crew/equipment: When Roy and Johnny climb up the open drawbridge, just as they reach the top and see the car dangling off the edge, when Roy says "Boy," the second cameraman is visible behind Roy sitting on the bridge.
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: After Chet suggests to Johnny and Roy that they trade vehicles, as the camera pans out the reflections of crew and equipment are visible in the two hubcaps of Roy's car.
Other mistake: During the rescue at the top of the open drawbridge, in the shots of Engine 2 we can see the red, vinyl material with the company number imprinted on it, adhered to the front of the engine.
Other mistake: When Station 51 is dispatched to 'man trapped in vehicle', we can see the real Station 127's vehicle is still parked inside the apparatus bay, near the rear bay door.
Deliberate mistake: During the rescue of the car at the top of the draw bridge, The Boat approaches and radios in to say that they have a diver standing by. Then after Johnny shouts, "Are you all right?" the rescue boat is shown again, but this time it's a flipped shot - note that everything is reversed from the prior shot.
Visible crew/equipment: After the rescue on the draw bridge, when Squad 51 gets back to the station Roy goes to the backyard and sits in the sports car, and in this shot just as we hear Johnny's footsteps, on the Land Rover's window we can see the reflection of a crew member who is moving backwards.
Visible crew/equipment: When Johnny and Roy are at the top of the open drawbridge, beside the car hanging over the edge, just after Roy says "Be careful, this could go at any minute," the moving shadows of the cameraman and another crew member are visible on the bridge surface. That shadow is visible in two other previous shots from the same angle.
Continuity mistake: When 51's guys are at the table eating and discussing Roy and Johnny's deal, Johnny tosses his car keys to Roy, and in the following shots those keys vanish and reappear on the table repeatedly, and in the shots where the keys appear on the table, it's the ketchup, mustard, and napkins that have vanished. Also notice that the ketchup's brand name is covered.
Deliberate mistake: When O'Brien shows up at the nurses' station for Dixie's answer, after she declines the offer Dixie walks off to a patient who's brought in by the police, and the last closeup that's shown of O'Brien is flipped - note his hair is parted the opposite way and the background is backwards.
Revealing mistake: When Johnny and Roy are at the top of the open drawbridge, Johnny is wearing a watch on his left wrist, but when his stunt double rescues the woman in the car dangling off the edge, he is not wearing a watch. Additionally, the stuntman's pompier belt has a large axe sheath attached to it, but Johnny's life belt does not, and the stuntman's arms are much hairier, as usual.
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 ★