Can of Worms

The guy next to me in Panera just said "I don't mean to cut my own thumbs off but...."

I think that is the worse expression I have ever heard in my entire life. Sir, please put down the metaphorical knife. Besides, once you cut off one thumb, I imagine it would be difficult, nay, impossible to cut off the other. So, sir, your turn of phrase is illogical in addition to being disgusting. Please stop talking.