I agree with @SpaceplaneAddict, that KSP, being a sandbox game (even in career mode really) has far too many possibilities for there to be a single storyline. People should make their own stories, rockets, spaceplanes, and whatever else they want. There are plenty of great stories in Fan Works and Mission Reports, just read some and if you're inspired, maybe make your own story. I think that's part of what makes KSP so awesome, the fact that you have your own space program, an arsenal of parts to play with, and a whole solar system to explore. You can do whatever you want, there's no storyline to follow, you can imagine what the Kerbals talk about while floating in their space stations or walking on alien worlds. I think that while a kerbal movie would be fun to watch, it would detract from the freedom KSP offers. I will say, though, that if they ever make a movie about me, I will demand 100% accurate orbital mechanics and star/moon/planet positions in the night sky, and that there be KSP references.