She's so skinny, if she stood sideways and stuck out her tongue, she'd look like a zipper. (That's a zip, for all you UKers.)

You're about as dumb as a bag of hair.

I you had a brain, it'd be lonesome.

You ain't got the brains God gave a duck!

Yer aboot as thick as twa short planks.

You are a lying sack of Siberian seal shit.

Damn! The hurrieder I go, the behinder I git.

Why don't you go take a long walk off a short pier?

Six and twa threes. (Scots for six of one and and half a dozen of the other.)

Cheerio the noo

SND