MALAPHORS

From Grammarphobia, one of my favorite sites:

A malaphor is a merging of two aphorisms, idioms, or cliches;  a blend of the words malapropism and metaphor.  The word "malaphor" was coined by Lawrence Harrison in his 1976 Washington Post article Searching For Metaphors.  one example:  "That's just the way the cookie bounces." 

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)