Two hands butter!

In the middle of the usual dinner time mayhem, the boy picks up his cup of chocolate milk and proceeds to drop it and spill it everywhere. Nothing too out of the ordinary until his little 2 year old sister starts reprimanding him-

Two hands butter! Two hands!!

Neither hubby nor I can control our laughter which infuriates the boy. He retorts- if this is so funny, you clean up the rest!