Ernie has a black eye about a second before the fight about the check even starts.
When Ernie falls down the manhole with Peter he has two cuts on his stomach, but when he comes up from the sewer water, the cuts are gone. He also gets bitten by a crocodile and has a chunk of his feathers ripped off, yet when he is climbing up the ladder, the mark that was left is gone.
The first time you see the sign to 'Morningwood Academy' there is an inscription saying 'No Irish' which is crossed out and amended to 'Irish ok'... After Chris spends his first night and is beaten for being poor, the next morning the sign to 'Morningwood Academy' has no inscription about the Irish.
During the first fight with Ernie, when the subway comes above ground, the people it runs over just disappear.