This is further to the post about Dr Who’s references to other sci-fi and some very knowledgeable comments, one of which pointed out that sci-fi movies owe a fair bit to Dr Who.
Spotting the refences and cliches makes up a good part of the enjoyment of sci-fi. There’s an inclusive list on cthreepio among other sites. Here are a few of my own favourites:
All alien races speak English. This is very convenient, of course. (Although, unusually, Klingons do have their own language.)
The most advanced computer can be completely confused into breaking, by being asked to process a contradictory statement.
Any high spec computer will become sentient. And homicidal. It can then only be defeated by making use of the surprising design fault listed above.
Non-humans usually look exactly like humans or exactly like humans with insect heads or with some wierd ear, nose, eye or forehead attribute.
About 70% of all non-earth civilisations are identical to those of medieval Europe. A further 20% are basically the same as Ancient Egypt.
The crew of any spaceship will happily mate with non-humans but there is less than 1% chance of crew members of different earth “races” ever getting involved with each other. Which is odd, given that space travel is only achieved when the earth becomes one big happy international family.
The holodeck is always broken in such a way that game characters will come to life and threaten the life of the crew, while the crew will never be able to end the game. Nevertheless, the holosuite is never dismantled. The crew will still go blithely into it. They will always choose Nazi Germany or an interplanetary war or some other blatantly dangerous setting.
Any Stargate crew member that you’ve never seen before who speaks a few lines at the beginning of an episode is doomed to die in the next few minutes. Being assigned to SG6 is a death sentence