They want it, man. I'm surprised he hadnt sliced it off yet. You are very susceptible to counterattack if anything goes wrong. Pick a chant that you like and keep it consistent. If they use one such as "One two three four, let's have a thumb war, five six seven eight, I use this hand to masturbate", you don't want that to throw you off your quick attack or quick dodge.
Polydactyly is relatively common in what comes to deformities, it's a dominant trait usually.
The photo is real, it's a polydactyl thumb. I'm imagining a hand tailor made for the original NES controller. Sometimes I go without for a few days and sometimes do it multiple times a day. Why didn't I ever think of that? After all, who among us hasn't been three belt notches deep in a stiffy and on the precipice of giving old Mr. Evil people gain power because otherwise-good people actively help them along.