This page explains in detail the interactions between the Mario series and the World Gone Sour series.
World Gone Sour[]
December 20, 2011
Upon encountering the gum enemies in the first level, the narrator says: "You can jump on these to kill 'em? What? Like mushrooms!" This is a reference to the Goombas, the mushroom enemies in the Mario series, that are killed by stomping on them.
License[]
The creators of World Gone Sour didn't hold any right over Nintendo's Mario, but they only included a minor reference to the series.