As Greg walks down the stairs exiting his first day at middle school a black girl walks out of the entrance 4 times as Rowley says "hey Greg, wanna come over and play?"
When Colin and Rowley have ice-cream, they never actually finish it. The second the shot cut, the actors handed them to a prop guy who then threw them in the bin. Then when the next shot began the prop guy ran to the closest freezer, which was about 100 metres away, made the ice creams as fast as he could, and ran back and handed them to Colin. This went on for half an hour. Just saying, they could have moved the freezer.