TCJ.com has a long interview with the one and only Sergio Aragones. Conducted by comics historian R.C. Harvey, it touches on Aragones' work in a thorough and detailed manner.
"To that classic inquiry—Where do you get your ideas? —Sergio has a playful reply:
"'When kids ask me, I tell them—Well, they’re floating in the air like little balloons. There are little balloons for musicians and there are little balloons for writers and for sculptors and for poets—whatever you are, you just pick your balloon and use it. I’m a cartoonist, and the sky is full of little balloons full of gags, so I just pick the ones I need. And I want to do it before somebody else picks them, so I’m there fighting to get the best ones.'
"Sergio laughed. 'No, I get ideas from where everybody else gets theirs. You sit there, and you work at it. There’s no magic; there’s no mystery. You sit, and you think.'"