During the prison break scene while Lydon tells Chloe that Petrus has been killed the baby is suspiciously quiet. The babe's raised hand clearly looks like a doll's hand.
When a dead dog is shown getting buried in rubble, it's obviously breathing as the rocks on the dog can be seen going up and down slightly.
When Lydon, Chloe and Nydia take refuge in Philos's house after the raid against Christians, there is a Latin alphabet painted on the wall behind them. This alphabet includes the letters J and W, which are totally unknown at the time and don't appear before the Middle Ages.