The resulting shape resembling a polygon with as many sides as there are participants.
Ste: "The rest of the rugby team are coming over later, but I've got no idea what to do for entertainment."
Tim: "More than five of you? You could always get a Bumagon going."
3 or more bums face inwards forming the segments of a tangerine. This is often enjoyed by being penetrated through the middle via tongue finger or penis.