butters both sides of the bread

a bisexual person that regularly partakes in hetrosexual and homosexual experiences

Phil: i saw mike holding hands with jim. last week he was fucking that girl.
Joe: didn't you know he butters both sides of the bread

Buttering both sides of the bread

To go much harder than is necessary. Worthless overachievment.

"Aww man, I studied for three hours and the test turned out to be easy! I really buttered both sides of the bread on this one."

"Dude last night I took ten viagra before fucking my girlfriend!"
"Woah man, why you always gotta be buttering both sides of the bread?"