Tim's pants split all down the front of one leg when Bill accidentally rips them off in falling down the hole. However Tim puts them back on later and they are completely undamaged.
Bill drops a lamp down to Graeme while he is in the hole. The lamp is later shown as working, even though the hole is a prehistoric cave with obviously nowhere to plug it in.
Bill mispronounces Oligocene Period as "oh-LOG-ih-scene" Period.
At one point Bill says his suction boots are stuck to the floor, and tries to pull one of his feet loose with no success. A split second later, when Bill and Tim get into a disagreement on who is going down the hole first, Bill shuffles his feet nervously and forgets to mime they are stuck, visibly lifting one of them. Right after, he mimes he has to "tug" on them to get them loose so he can walk to the hole.
The dinosaur's mouth in the scene where the boys get "eaten" and the dinosaur's mouth in the scene where Bill is using the vocal chords to help amplify his voice, while supposed to be belonging to the same dinosaur, bear no resemblance to one another. One is square with conical teeth tightly grouped together and one is the proper rounded T-Rex shape with smaller, wider-spaced triangular teeth.