8 Movies That Completely Ignored Important Plot Points
7. Alien 3 - The Sulaco's Egg
Literally the entire plot of Alien 3 is kicked into motion by a lone Xenomorph egg that hatches aboard the Sulaco transport ship, but the how and why of this egg's placement isn't something the movie cares very much about.
In the opening few seconds, the egg hatches and sprouts a facehugger, which impregnates Ripley before its acidic blood causes a fire and sends the ship's passengers plummeting down to the surface of Fiorina 161.
This is where the rest of the movie takes place, so without that egg there wouldn't even be a plot, and yet, Alien 3 offers no explanation as to how the egg ended up on the Sulaco in the first place. The movie just opens and it's already there, despite the fact that Ripley killed the alien queen at the end of Aliens, and there was no indication that the Sulaco contained any danger whatsoever.
Over the years, fans have come up with dozens of excuses to mask this ignored plot point (maybe Bishop planted it, maybe it was on the Sulaco all along, maybe the queen sneaked it onboard) but they're all quite flimsy, and when there's this much confusion over something, you know the movie is at fault.