Other mistake: During the structure fire, when Engine 98 rolls up we can see the large red vinyl adhered to the top of the engine's cab. Then, when Truck 106 rolls up we see its company number 106 on the door, but in the overhead shot we can see the number 8 on the roof of the cab, not 106. This presumably means that the door has one of the prop dept's magnetic decals imprinted with 106, and the roof still shows the Truck company's real number.
Other mistake: After finding out about Valerie's three kids, when Johnny and Roy are sitting in the station's locker room at the start of their next shift, there are a few moments during this conversation where Kevin Tighe softly mouths some of Randolph Mantooth's lines as Johnny is speaking, particularly when Johnny says "Beautiful chic."
Other mistake: After Station 51 is dispatched to the structure fire, just as Roy and Johnny start heading upstairs we see footage from 4x3, "Gossip," when Johnny brings the hose to the stairs at the chemical fire, but the line doesn't reach so he leaves the hose at the bottom step, and they continue up.
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 ★