Character mistake: When Stan inflates himself, Michael asks, "How'd he do that?", implying that he doesn't know the rules of the Looney Tunes world. Since Michael was rolled into a ball by the aliens earlier in the film, this shouldn't be too much of a surprise.
Suggested correction: When Michael was rolled into a ball, he wasn't concerned with how that was possible and soon after he forgot about it. He was more concerned with dealing with the Monstars at the time and, in particular, helping his cartoon friends preparing for the game. When Michael witnessed Stan being flattened and inflated, it looked particularly strange and unfamiliar to him, unlike before as he couldn't watch himself experiencing being rolled into a ball. And that is what triggered his response about questioning how it was possible.