Plot hole: When George stops the machine for the first time, the candle burned down to about half of its size, which took according to his observations 98 minutes. But as the trip continues it takes seven hours for it to burn down completely. (00:25:45)
Revealing mistake: When the two dinosaurs are fighting besides the cliff, Malone and Jennifer Holmes hide behind a rock overlooking the cliff. One of the dinosaurs sweeps its tail, and knocks the two lovebirds over the cliff, but they fall onto a rock jutting out from the cliff. After we see them fall, there is a wide shot of the dinosaur swinging its tail. He swings it one way, then the other. After he swings it the first way, the tail freezes in mid-air for a split second, then swings the other way. It's obviously the same shot of the first tail swing, but played in reverse with a pause in between.
Continuity mistake: While Major Allison is piloting the X-80, the style/model of the aircraft differs in shots, and two different numbers appear on its body - FC-226 and FE-229, as well as four different tail numbers that appear on its tailfin - 62216, 70236, 70229, and 61226.
Continuity mistake: When Robot ZX29B is coughing up the rubbish that Bugs fed into him, there are three trash cans behind him, but when Yosemite Sam sees the robot on his monitor, there is only one trash can behind him.