When Commander Weldon exits the rescue helicopter, he removes his yellow safety vest; then, after the scene cut, he removes it again.
Amy Martin's hairstyles, during and after Grover's escapade, go from straight/flat, to flipped up, to very wavy, back to straight/flat. Hair color also varies.
When Grover is floating around in the balloon harness towards the end of the film, as he nears a building with a brick facade, a shadow of the rigging being used can be seen above the balloons on the brick wall.