We have a student that's still in the recently-post-pubescent spiderlike stage of development - arms and legs everywhere. With a hakama on he bears a rather startling resemblance to a featherduster.
He's also darned near double-jointed; which makes some techniques rather odd when he's uke. I remember once practicing with him; I was performing katate kosa-tori kokyunage. It was working - sort of - but with those arms going off in all directions I wasn't getting the drop required for an effective finish. The resulting technique was hilarious - as he came around and his arms came up; I caught them; folded him up like a jointed ruler and then
dropped him. Not much to read; but it looked funny as hell.