A malaphor is the unintentional blending of different phrases or metaphors, such as "It's not rocket surgery" or "He smokes like a fish" I'd love to see some that you have actually seen, read or (better yet) used. My favorites are; That's the way the cookie bounces. (I use that one regularly, just to see if people will notice.) Take a flying hike. What are some of your (clean) favorites?
He was three sheets to the mattress. You're the apple of my pie. It's raining cats and mice. You don't have a floor to stand on. That idea is really off the ceiling. That's music to my speakers!
putting out fires with vaseline for bitter or worse, in sickness and in hell having a sneezure deceased & desisted odor of a lonely heart
Mine is one that's already been mentioned here (sort of): That's a horse of a different kettle of fish.