To bell the cat

 
"Belling the cat" or "to bell the cat" is an English colloquialism that means to suggest or attempt to perform a difficult or impossible task.

The phrase comes from the Aesop's Fable The Mice in Council , in which a group of mice declare that the only way to avoid the dangerous cat is to tie a bell around its neck in order to give warning whenever it is near. One mouse then asks who will perform the dangerous task. The moral of the story, as commonly given, is that it is easy to suggest difficult (or impossible) solutions if the individual giving the solution is not the one who has to implement it.