The lobster disappears before the boy decides to leave with one of the shells.
After the spaceship is taken to the house--shaken quite a bit--all of Mark's tools are still in place on his workbench.
The hearing aid prop used by the actors playing giants is only about 1/2 the scale of the one used by the actors playing the little people, who are supposed to be 1/12 the giants' scale. Thus, the hearing aid seems to expand enormously when handed from a little person to a giant.