Happier'n a dead pig in the sunshine.
As confused as a runned over dog.
Crazy as a road lizard.
His brains would fit in a thimble and roll around like a BB in a boxcar.
Too fat to ride in the front.
Colder than the Devil's heart.
Hotter than the Devil's underpants.
So dry the catfish have ticks.
So wet the catfish are climbing trees.
Stupider than Uncle John's prize goat.
He'd a' been a lot taller if he didn't have so much turned under (big feet).
He's about two sammiches shy of a picnic basket.
His elevator don't go all the way to the top.
She's so ugly she has to sneak up on a glass of water to get a drink.
and the one I learned here:
Darker than the inside of a cow.

And by the way, it's not "Carter's Liver Pills". It's "Carter's Little Liver Pills".
https://en.wikipedia.org/wiki/Carter...le_Liver_Pills