When Roy Bullock first meets Buttermaker, Greg Kinnear (Bullock) flubs his lines. He says, "stop by and see me sometime, I'm over at Chevy Valley Subaru." The name of the car dealership, as referenced later in the film and as makes sense with standard naming convention, is Valley Chevy Subaru.
Garo bats in front of Kelly twice, getting hit by the pitch once, and making out once. Then in the final inning, he hits after Kelly, an unacceptable change in the batting order. There is a way this could have happened under Little League rules, but it would have required Garo to be removed from the game for a substitute and to then return to the game and replace someone else. That didn't happen.
It is revealed that Buttermaker only pitched two-thirds of an inning in the majors, and left with a 36.00 ERA. This is statistically impossible, as a pitcher completing two-thirds of an inning must have an ERA that is a multiple of 13.50.
No less than four times does Hooper roll his wheelchair to the left to exit the dugout. Given that there are steps this would make his exit a little tricky. However, on the third base end of the dugout in the championship game it is clear that Hooper rolls down a ramp.