If someone asks, "How are you?" Granny always said, "Fair to middlin'..."
I saw the mule one a few posts back, always heard it as "grinnin' like a mule eatin' briars..."
"Gone quicker than a cricket in a brim bed"
"That thing ain't got enough power to pull a greasy string out of a cat's ass"
"He's as goofy looking as three legged cat trying to bury a turd on a frozen pond"
"This is harder than finding a hotdog at a PETA meeting"