Two Armypeople of hispanic descent that spend their time playing DefJam Rapstar;not properly master the Ghetto slang and or think that they have reached their inner Gangsta.
FBpost: "Played some Def Jam Rapstar with Buttercups... Rocked the mic...forshizzl my nizzl."
Buckle up Buttercup is a sarcastic expression, denoting that one should get ready for some upcoming unpleasant or extreme action.
It is a bit of a sarcastic portmanteau between the "buckle up" phrase used to get people to use seat belts and "pucker up buttercup" meaning to prepare for a kiss. The sarcasm reverses the positive connotations.