To let the cat out of the bag (To tell something that was supposed to be kept secret, like telling the recipiant of a surprise party that there is going to be one.)
To leg out the cut of the bug (Ooooh! I'm running because that bug bite hurts so much.)
(I didn't see anything funny from swapping bag and cat, but by swapping a few letters I think it might be. To "leg out" is a baseball term meaning to run to first base before the ball gets there.)
'Share and enjoy'