I think I remember an awesome Def Leppard song from the 80s called "Autograph." (And why couldn't those hair banders spell? Huh?) I never went to their concert or even wanted their autographs, and I'm pretty sure they're all driving minivans now and busy on the weekends painting lawn furniture with spray paint cans...
Autographs in the sumo world happen, like everything else sumo, big time. Instead of a mere signing of the name, the guys make an actual hand print with either black or red ink. It's called a tegata, which means hand shape. I don't know, but I'd guess they do it on rice paper.
This one belongs to Kotomitsuki, who (as of today) is the highest ranked Japanese wrestler in the lists. He's an ozeki east, "champion," ranked 4th overall. Only the top tiers of wrestlers are allowed to make and distribute the autographs. The squiggles on the side are the kanji (Japanese/Chinese characters) for the name Kotomitsuki. No, I can't read those particular characters, I'll freely admit. But don't they look cool? Here's another one (I grabbed it from wikipedia) with the red ink.
I bet the ink gets on their kimonos. And I bet it's hard to get out in the wash.