Planet of the Apes/Fridge

The 1968 film

 * The chronometer showing Earth time is still working after the rest of the ship's power fails (in plot terms, Taylor has to see it immediately before he leaves the ship).

Escape from the Planet of the Apes

 * The humans learn that in the future, apes will talk and treat humans like animals. So they want to prevent Cornelius and Zira from having descendants as their descendants would probably be talking apes. They fail. But does this mean that Cornelius and Zira are their own ancestors?
 * No, because the origin story they told (of an ape slave who one day said to humans what had been said to him a thousand times over - "no") is different from what came to be after they traveled back in time - their son Milo/Caesar became the savior of the apes instead.
 * Probably not. Other chimps evolve by the time of the next film, after all.
 * And their son, Milo,.
 * On another point, it strains credibility (to say the least) that Dr. Milo would be able to raise Taylor's ship from the lakebed, refit its blown hatches and get it working again, just in time to escape the Earth's destruction. Of course, without that rather huge implausibility there'd be no movie, so...

The 2001 remake

 * The humans and the apes are descended from the crew of the space station. Where did the horses come from?