Revealing mistake: After Johnny joins Roy in the ambulance and the patient flatlines they continue to Rampart, and when Brackett asks 51 for a strip, if we look out the window that's beside Johnny, we can see GlamourTrams in the distance. And when Roy says, "Isopeterenol drip, 10-4," we can see GlamourTrams right outside the window. They are driving around Universal's lot while shooting the footage inside the ambulance.
Visible crew/equipment: When Station 51 is dispatched to the motorcycle accident, just as Engine 51 rolls out of the apparatus bay, the reflections of array lighting and two reflector screens are visible on the side of the engine.
Visible crew/equipment: At the scene of the motorcycle accident Johnny contacts Rampart, and when Dixie opens the door to the base station booth and walks in, the outlines of the lavalier mic transmitter and wire are visible on the back of her uniform.
Continuity mistake: On the airplane, when Roy asks Johnny if he knows the flight attendant's name yet, the headset is around Roy's neck, but in the closeup it vanishes, then next shot it reappears again.
Visible crew/equipment: At the station, when Johnny and Roy talk about The Stewardess and then while Chet is mopping the floor, the bulging outline of the mic transmitter is visible on the front, left side of Roy's shirt, above his belt.
Visible crew/equipment: In the ambulance, when Roy administers the bicarb and then the isoproterenol IV, the outline of the mic transmitter is visible on the left side of the third paramedic's shirt, as he's doing chest compressions.
Continuity mistake: During Johnny and Roy's flight to LAX there are a few shots of the airplane in mid-air and when it lands, and the type of airplane changes - note the engines and tail.
Visible crew/equipment: At the start, when Johnny is telling The Stewardess about the underwater rescue and in following shots, the outline of the lavalier mic wire and the dark strap (that holds the transmitter) around Johnny's waist are visible on the back of his shirt, and the mic transmitter is visible on the front, left side of his shirt, above his belt.
Visible crew/equipment: After the airplane rescue, at Rampart when Brackett congratulates Roy and Johnny on a job well done, the outline of the mic transmitter is visible on the front, left side of Roy's shirt, just above his belt.
Continuity mistake: When transporting the heart attack victim from the plane the ambulance starts as a Ford and ends as a Chevy.
Continuity mistake: Marco's mustache goes missing when Station 51 is dispatched to the structure fire, but then it reappears.
Visible crew/equipment: When Johnny removes David's red helmet after his motorcycle accident, the reflection of array set lights are visible on the red surface.
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 ★