The English phrase: To be in cahoots with someone, to be in bed with somebody. It suggests in German: Mit jemandem unter einer Decke stecken (essentially: to stick under one covering).
One hilarious German expression for the English idiom: Piss off! Nuts to you! = Rutsch mir den Buckel runter! Its literal definition is: Move down my back!
English expression: All hell breaks loose, to celebrate, to have it going on. A funny German phrase is for example: Da steppt der Bär (literal translation: the bear is tap-dancing)