In the scene where Lois disinfects Stewie, at first the chair to the right part of the screen is seen brown, but afterwards, the chair is then seen blue. Also, the three cotton balls disappear after the same scene.
In Connie's car, Chris removed his hat and the bat on his head goes out the window. But the window is closed so it would not be be possible for it to escape.
At the 5:49 mark at James Woods High, a kid walks in front of the flag pole but the original perspective places him several feet behind it.
When Stewie bullies Brian, Brian has no tail.
After bulking up, Stewie takes the TV remote off a table that is to the left diagonally in front of the couch. The table then moves back a couple of feet closer to the couch.
In the living room after Peter tells Lois he put Stewie on steroids Brian disappears from the middle cushion of the couch and then reappears there in the subsequent scene.