Revealing mistake: When McCreedy flashes back to when he first saw the Hobgoblins, the magazine he is reading in the flashback obviously has no pages. You can tell when he closes it and sits it down that that the inside covers are blank too.
Bug: If you summon any large vehicle and lay it on its side and get in and out of it, you may fall through the ground. If you use an ornithopter (maybe other flying vehicles as well), you can fly inside the ground and emerge anywhere.
Bug: In Action 8-8, destroy the two spikes with a black hole and tap the red beam blocking you from grabbing the star with your stylus. Create a box and place it below you. If done correctly you should go through the ceiling and pass the red beam, allowing you to grab the Star.
Bug: In Action 1-7, ride on a camel and head toward the tornado. Keep going right and eventually you'll go through the ceiling. Sometimes you'll die and other times you'll land and will be easily able to grab the star.
Bug: In the Playground (title screen) lasso yourself to a trampoline and then bounce on it. Since you are hooked to the trampoline, it'll stay under you when you bounce and you'll keep going up and up and up.
Continuity mistake: In the scene where Preston is being chased at the restaurant, the water sprays turn on and the bad guys fall over including the banker. We see him get back up. But immediately in the next shot, he is back on the ground and is getting up again.
Continuity mistake: When Preston's dad walks into the room on Mr. Macintosh's birthday, and he mistakes Preston in a big desk chair for Macintosh, his hands keep alternating from side his hips, to in his pockets, or by his ankles.