By definition the sickest sexual act in mankind's wide repertoire of deviance. Involves any sort of sharp objects, though most commonly scissors, rubberbands, and a pineapple. Note that one's whole body should be disinffected before attempting a mackson.
My kids actually said that they'd rather eat the cardboard box as it probably had more flavour than the shit posing as food it contained! True! They've called it Muckdonalds ever since.