Nasima, it's a saying generally known as an idiom which is not taken literally. A similar idiom would be: "I'll eat my hat". As Lucy Jean said, the one Julie used comes from "Well, I'll be a monkey's uncle" but since Julie is a female, she changed it to aunt. These expressions of speech make the English language interesting if you know what they mean but make it a real pain if you're trying to learn the language. Hope this helps. :-)