From my art tumblr inbox:

Keith/Silver Skater origins? - Anonymous

KEITH: Okay, like, so, somewhere waaaay out there in the universe is this planet of highly intelligent life-form dudes, right? Except these super genius alien guys kinda all look like liquid metal goop.

SYM: ...

KEITH: Dude, I don't care how super-involved you are. You're still goop. So, because these guys are, y'know, all curious about the mysteries of the universe and stuff, sometimes they put a couple explorer-goops into these super-cool-looking metal football bullets and shoot them into space at planets they wanna know more about.

SYM: ...!

KEITH: "Streamlined conveyance module," my striped butt! It is -so- a football, dude! I -showed- you what they look like! You thought the whole sport was some kinda space program training for weeks! Can I keep going?

SYM: ...

KEITH: Awesome. So, like, one of these -football bullets- got shot to Earth and, like, totally survived slamming through the atmosphere before sailing through a window I had open and into a basket full of laundry I was totally intending to get to.

SYM: ...!

KEITH: It was only a couple of days, sheesh... Anyway, so I pick up the basket to do my laundry, but I don't see the silver space thing buried in there. But suddenly it cracks open like a metal egg from intergalactic hell and this shiny goop just lunges at my face, right? And I'm like, clawing at it and screaming and tripping over stuff, and then it was like, gone? Turns out that even though they're, like, super-evolved, they can't survive by themselves for very long on different planets and gotta glomp onto the first intelligent native they can to survive.

SYM: ...

KEITH: ...Hey! I thought super-intelligent aliens didn't -make- mistakes, so there! Anyway, so like, in exchange for helping Sym stay alive and gather information about our galaxy and stuff, he totally covers me and my board in this super-invulnerable shell and I can fly and shoot lasers from my eyes! It's pretty awesome. Oh, and I still got the metal football bullet on my dresser.