I just heard someone say, “Don’t bite the gift hand in the mouth,” with total seriousness. I’ve also heard, “It’s a doggie dog world,” and “Tic for tac.”
Have you ever heard someone mix or mangle a metaphor? I need your examples, because I can’t stop laughing about this.
Now I want to tell someone not to bite the horse that feeds you.
Not as dramatically mangled, but my wife has a habit of saying someone’s going or talking “ten to the dozen”, and gets quite indignant when I point out that would mean the exact opposite of what she intended.
I once overheard a man saying, “Well, now the ball is in his lap!” Yes, it certainly is.
I heard a buddy once say, the morning after a long night of drinking, “Man, I’m hung over like a horse!”
I love mangling them on purpose.
“We’re just two ships that go bump in the night.”
“Half of one, six dozen of another.”
I once remarked that something was as likely to happen as “a camel passing through the knee of an idol.”
Always been fond of:
“We’ll burn that bridge when we get to it.”
You can say that again.
My favorites are “It’s not rocket surgery,” and “Does the pope shit in the woods?”.
I’ve see both on these boards, especially the former.
My wife always says, “Half a dozen of one, half a dozen of the other.” Huh?
She’s a smart lady but a real font of malaprops. One time she was talking about Kate Middleton and said she was “a very stealth woman” when she meant to say “svelte”. Another time she said that no matter how angry she was she would never “cut off her nose and spike her face” (good advice no matter how you put it”. Then there was the time our friend’s son came home after he had run off with a girl. She talked about how “the probable son” had returned.
I love her but sometimes conversations can be very unusual.
So have I. 
Yep. Also “Mind like a steel sieve.”
FTR, I invented both of those.
I recently mixed up “lies like a trooper” and “swears like a sailor,” to get “lies like a sailor,” which my sailor friend resented just a bit. Oops.
I am a fan of saying that someone is “not the smartest knife in the drawer.”
:dubious: I never heard any of those. Now, “swears like a trooper,” that’s a thing. (You get bonus points, though, for not putting “trouper”.)
Smokes like a fish.
Drinks like a chimney.
Make like a tree and get out of here! (from Back to the Future)
About 20 years ago, in an interview after an NBA win, I heard a player say, “After all the chips fall, the cream rises to the top of the crop!”
What is she going for?
In a similar vein, a personal favourite (not mine - stole it from Pratchett): “we’ve passed a lot of water under bridges since then”.