You need to get your ass together

This is a mash up of “get your act/shit together” (get organized) and “get off your ass” (stop loafing and get to work).  Both idioms direct someone to get moving, invoking a congruent conflation.  Also ass and act are three letter words that have a similar sound.  Finally, the lower half of the body is at work here in both phrases.  Many thanks to Robyn Pietrucha for blurting this one out and passing it along!