Qui-gon follows Obi-wan out one night because he's worried about him sneaking out so often. He follows him to a nightclub and some spying reveals to him that Obi-wan likes sucking off strangers through glory holes in the bathroom. Qui-gon can't resist temptation and puts himself in the hole.
Qui-Gon/Obi-Wan - Glory Hole - Poss. dubious consent.