While "Alien" (1979) is widely considered to be among the most important sci-fi films of all time, it features an absolutely glaring, unforgivable error in its first scene.

The film opens as we slowly explore the dim bridge of the star freighter Nostromo, empty with its crew long in hibernation. We pan the creepy interior, which includes a classic bobbing duck toy busily bobbing into a small container of liquid. And ... wait a sec. Hold everything!

The crew is in hibernation. That appears to be an ordinary container of what is probably water, sitting alone, unconnected to any tubes, pipes, or other infrastructure. Any liquid in that container would evaporate completely in a matter of days. If the duck can't dip into liquid to moisten its beak, it will stop bobbing.

There's nobody around to refill that container, no sign of any mechanism to do so.

This shameful lack of realism could have ruined the entire film. Luckily, most people didn't notice this nightmarish error.