I see my brother regularly; let’s call him Yan. Yan is a famous curmudgeon, dissatisfied with just about every movies, TV show, or book he’s ever digested, and we often have long talks about what he doesn’t like about The Entertainments the universe offers him. He’s usually pretty savvy in his criticisms, though I’m more forgiving and can accept imperfection as long as there are compensating pleasures offered and so we don’t usually agree on what qualifies as ‘good’ in TV or movies.
One of the things we often discuss is a tendency by bad writers to view any Science Fiction or Fantasy story as a license to do anything, to toss out the very laws of physics. I’m not talking about magic here, you see – I’m talking about the assumption by hack writers that just because a story is SFnal, anything can happen. It’s one thing to have magic in your story. The Jedi can do just about anything, okay, fine – that gets established early on in the Star Wars world and so when Yoda lifts the X-Wing out of the swamp, or when Vader chokes the life out of someone who’s on a completely different ship, well, you just shrug and accept it. The rules of The Force are established and that’s fine.
Sometimes, though, you have writers who decide that just because you have, say, a psychic or a spaceship in the story, well, anything is possible. That if a character has one special power or ability, he or she should be able to sprout new ones whenever the plot requires a solution. Of course, sometimes a character with unspecified abilities can believably display a heretofore unknown aspect of them – take Spock stuffing his soul into Bones McCoy in Star Trek 2 – so to a certain extent it depends on how it’s handled.
For the clearest example of the acidic effect this attitude has on SF writing, I direct your suffering eyes to Highlander 2: The Quickening. The special sauce of this movie is the idea that since it’s a SF story, anything goes! And I do mean anything. Though to be fair this movie apparently suffered from meddlesome investors who took a bad movie and made it indescribably terrible, the fact remains that the writers of this movie heard ‘immortals’ and ‘science fiction’ and decided that whatever batshit crazy stuff they came up with would work.
You can, of course, let your imagination run when writing SF/F work, but there have to be rules of some sort. Especially in serial works when a character has, say, dozens of episodes or novels to develop and display their abilities. Suddenly granting them the one power which would solve your plotting problems will not fly, my friend. But then, my brother and I are bitter, bitter people. For example: I still intend to get my $7 back from the producers of Highlander 2. Oh, some day, they will pay me back. I swears it.