First of all, watch this:
Now, I realize the above clip is meant to be humorous, and it is, though I also got a separate and equally valid lesson in it, which is that certain genres do not do well when combined together. I can only name a few instances where combining aspects of fantasy, science fiction, cowboys, horror, you name it, has turned out well.
Whenever a Star Trek episode veers into a holodeck, the story rapidly declines into Suckville. Cowboy vampires, robots with swords, dragons in the present, these all sound neat in theory, but when put onto a screen or in a novel, you end up with campy crap.
I don't know why that is. Maybe the dissonance between discordant images shatters any suspension of disbelief the audience has built up over the years. Perhaps we can take bloodsucking fiends in one movie, and guys with lasers in another, but when you combine the two into vampire cyborgs, we step back and think, "Hey, that's lame," which is shorthand for when we deny the piece any plausibility.
So it works in the video above, but if anyone is thinking it would be great to make a science fiction musical theatre review with knights and dragons, please reconsider. The world will be a better place if you don't.