Odds of Getting In
Becoming a card-carrying, spacesuit-wearing NASA astronaut is about as unlikely as shooting a rocket randomly into space and hitting Jupiter smack in its eye.
NASA routinely gets thousands of applications for a handful of spots, and many of them come with résumé packed full of experience—scientists, military pilots, and anyone else relevant to the overall mission of space. The competition's fiercer than Beyoncé riding a lion (almost too fierce).
Let's say you get lucky and you actually get chosen to become a certified space traveler (now who's fierce?). You're still not going to space any time soon. First, there has to be an available mission and you have to be selected for it. The training is long and you have to endure all of it. Then you finally have to be given clearance aboard whatever other country's ship is heading up there.
It's cool though. There aren't any video games in space, so you can totally use your Earth-bound time to catch up on as many as you can (maybe start with EarthBound?).