research yields disappointing results. it appears to be impossible. https://wiki.bme.com/index.php?title=Testicle_Piercing warning: following the above link will lead you to balls.
Personally I can't think of much that's less likely to give me an erection than the thought that someone is about to push needles through my balls, still, it takes all sorts.
why are you asking us and why would we care? everyone has some kind of odd sex thing, so to each their own. i was sort of hoping this would be about some other kind of balls. the kind that tend to deflate when you do that.
I've a feeling the type of balls he's talking about would deflate as well with a huge hole punched through them...
Iv'e Got A Better Idea........Why Not Piece Your Ears Together...... Nothing Of Any Real Value Is Located Between Them......So No Harm Done...... Cheers Glen.