From Grammarphobia, one of my favorite sites:
Look at some of these funny, silly, and absurd examples of malaphors which is also known as "idiom blend":
"We'll burn that bridge when we get to it."
"You hit the nail right on the nose.", a blend of "You hit the nail right on the head" and "That's right on the nose."
"She really stuck her neck out on a limb." ("stuck neck out/went out on a limb)
"I can't make these split minute decisions." (split-second/last-minute)