This is a game that involves replacing a word or syllable in a popularname, title, or phrase with the word butt.
The Butt Game would result in people saying things like: The Green Butt Packers, The Empire Strikes Butt, Sargent Peppers Lonely Hearts Club Butt by The Buttles, Kim Kardashibutt, Luke Buttwalker, There's Not Enough Butt In The World, What's Butt Got to do with It?, Etc...
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.