Revealing mistake: The infant baby was computer animated in every scene in which the face appeared. Even the feet were obviously touched up by computer in the hallway scene. The lighting isn't quite right, the skin texture isn't quite right, and the child's face is just too animated.
Continuity mistake: As Theo is sitting down at his desk, the camera comes up from behind the woman across from him, who has small knick knacks and figurines covering her desk. The shot zooms in on Theo and then switches to the crying woman. When the shot changes, notice the "fat-baby" figurine suddenly switches with two-smaller animal figurines. It's hard to tell what they are, but it's easy to see they've been switched with the baby.