Hondo Flanks and Carrot Cake have Big Macintosh and Shining Armor over for some ‘male bonding’.
Seriously that's all there is to it, 100% clop with no social or moral redeeming value.
Contains: Cheating-with-permission gay horse sex, oral, anal, cum swapping, light humiliation, very light feminization (basically just everypony calling Shining Armor ‘Princess’), pile driver position, auto-fellatio, cum inflation, probably some other stuff I forgot.