Here's an idea for an ult.

Duck on Head - Can click on any champion (range 500). He becomes a 'turret' attached to the champion able to attack and cast spells at half damage. He can end the ult early to get down from the champion's head. While on an enemy champion, he lowers their Attack and Ability Power by (20/30/40 + 0.3/AP) . On allied champions, Schadadle tanks for the target, using his Armor/MR if better and dividing the damage between the two of them. Lasts 8 seconds. (Cooldown: 3/2.5/2 min)

I was trying to find a witty way to work in a munchkin joke but to no avail. I think it might be too good or just too strange.