Factual error: In the scene where Waternoose and Sully are talking, Waternoose gets himself some "coffee", which is sludgy and thick and takes quite a while to pour from the machine. Seconds later, he takes a very quick sip. Since the liquid was so thick and there was little in the cup, it would be impossible for it to pour that fast.
Factual error: The map of the world on the scare floor shows Australia without Tasmania. This is best seen late in the movie after Boo has returned home, Sully is now management and when Mike asks him to follow him you can clearly see the world map behind Sully showing Australia and no Tasmania. (01:23:30)
Factual error: After Mike rebuilds Boo's door, it shows a few crack lines but is otherwise intact. But the shredder created a lot of sawdust so it would be impossible to rebuild the door using only the wood pieces. (01:20:00 - 01:24:10)