Deliberate mistake: The Benchwarmers originally had only three players, and then only one who could actually hit. Despite this, none of the (supposedly competent) little league coaches chose to simply walk all the players and force an out.
Deliberate mistake: When Gus tapes Clark's hand to a baseball bat, Clark hits the ball but doesn't drop the bat, then he runs to the base and then he's safe. In a real game if you don't drop the bat it's an out.