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: When Yosemite Sam sends out robot ZX29B to capture Bugs Bunny, the robot hides by some dustbins by the dump and you can see there are two dustbins by him. When Bugs empties his rubbish into the robot, the two dustbins have disappeared, and when robot ZX29B coughs up the rubbish in the next shot, they are back again.