When Gomez (Fernando Lamas) is piloting the helicopter, from the outside he is wearing nothing over his ears; in the inside shot, however, he is wearing headphones.
From the outside of the helicopter Costa (Jay Novello) looks from a window right beside his seat. In the shot inside the helicopter, however, there is no window beside his seat.
When the explorers are scared away from their initial campsite beside the helicopter, it is nighttime; however, as they are running through the jungle it is daylight.
The scene of the first dinosaur, disturbing the campsite, uses the exact same footage of it crashing through the jungle four times before moving to another location.
In the exterior shots of the helicopter, Manuel Gomez can be seen in a tiny cockpit on top flying it (this also houses much of the rotor engine). When they approach the plateau, the interior cockpit expands to accommodate the Professor and the rest of the cast.
At the end of the movie the egg breaks open, revealing a little "dinosaur" inside. The professor declares it a "Tyrannosaurus Rex," which stands on its two large rear legs and had two small front legs that don't touch the ground. The lizard used in the movie, however, has with four equal-sized legs and looks like a baby alligator, which is what it really is.
When the camp is attacked, after the explorers have run away, Challenger identifies the creature as a Brontosaurus, yet the posture of the animal is all wrong and it has certain features from other herbivorous dinosaurs like Triceratops and Stegosaurus.
When Lord Roxton asks Gomez if he loves the guitar, he is not actually playing one as the sound it makes could not be made by the one he is holding, as it is a four-string guitar/ukulele.
Challenger constantly misidentifies the dinosaurs they encounter on the plateau.
None of the prehistoric creatures look anything like what they are called by the explorers. In fact, none are even dinosaurs: dinosaurs have legs which stand vertically beneath their bodies, while the lizards shown all have legs which splay out to the sides.
At the opening of the film a reporter says he's from the B.B.C. and is at London Airport which is confirmed by a large sign on a grass bank saying 'London Airport' in which case why are all the vehicles seen American.
When the explorers encounter the dinosaur in the "Cave of Fire," the wires holding the monster upright can be seen.
When the native girl waits for Jennifer to fall asleep, she tries to escape. In the scuffle to subdue her, one of the large boulders is moved by an actor. Such a large rock, when bumped, could not have moved.
When Gomez walks out into the jungle to scout around, he's suddenly heard calling out for help - but he's still seen walking calmly in the distance, unharmed and clearly not calling out at all.
In the scene where Ed Malone and Jennifer Holmes meet up in the forest before the "Brontosaurus" chases them, Ed Malone says dialogue, but his mouth doesn't move. Also, Jennifer's mouth moves, but no dialogue comes out.
At the end of the movie, as the group are exiting the passageway and after the smoke clears, you can see a crew member peering at them through the opening.
A headline announces "Challenger llega a Rio". "Rio" being Rio de Janeiro in Brazil, it is presumably a Brazilian newspaper, and the language of Brazil is Portuguese. "Challenger llega a Rio" is Spanish; the Portuguese would be "Challenger chega so Rio".
The government of Brazil, which has jurisdiction over the territory that Challenger and Roxton will explore, would logically be very interested in such an ambitious enterprise that affects Brazil directly. At no moment of the film, however, is the government of Brazil ever mentioned.
When the party of adventurers are in a boat approaching the dock where they will meet their helicopter pilot, Challenger is ostentatiously holding his large black umbrella up as a parasol against the tropical sun. However, the angle of the sun is such that no part of him is shaded by the umbrella.