Audio problem: When they scream at the cupcake shop, Gru sounds like he's behind the glass dome, while Lucy gives off a regular scream. But as we can see, Lucy is behind the dome, making a silly face, not Gru.
Audio problem: As Gru attempts the dance floor key, some of the guacamole from his nacho hat falls out of the hat and lands on one of the keys which then triggers one of the sound effects. An axe then chops off the rear end of his nacho hat and lands on the part of the dance floor behind him, but no sound effect is made from the floor. (01:04:05)
Chosen answer: The car is always shown in shots from the front so we can't see if the boot had a leak.
boss of epicness
If the boot had a leak large enough to admit the starfish it would have filled with water and Gru would have drowned.