like trying to nail jello to a cat

A merging of two popular phrases, each meant to reflect attempting something very difficult: “like nailing jello to a tree” and “like herding cats”. This version simply implies, humorously and a bit gruesomely, that one is, in fact, attempting the impossible.

John’s attempt to get this three kids to bed after they each ate a bag of Halloween candy is like trying to nail jello to a cat.