eat one's hat

If anybody could tell me precisely what the message was, I'll eat their hat.

I'll eat my hat if I ever see him crack a smile.

Your contract will be ready to sign before you take to sea again or I'll eat my hat.

"If they don't say raise taxes I'll eat my hat."

If they weren't talking about the crew from the University of Chicago, he'd eat his hat.

If that's not ten words longer than it needs to be, I'll eat my hat.

If they do, then I'll have to eat my hat or something.

And those look like stars or I'll eat my hat.

"If any outfit can lay that highway in less than three years, I'll eat my hat!"

The thin one's just finished a long stretch in jail, or I'll eat my hat.