A three way involving a Hermaphrodite, and two men (One man wears a strap-on). The Hermaphrodite gets on all fours, while the guy with the strap-on has sex with her doggy style. He penetrates both the hermaphrodites holes using his penis and the strap-on while at the same time giving the hermaphrodite a reach around. The last guy engages in anal sex with the strap-on guy completing the train. The train cannot be broken until all members have ejaculated (thus providing the gravy).
I was at a party the other day, and I walked in on your brother in an Illinois Gravy Train.