Humorous Idioms

I am privileged that one of my dearest friends often shares the memories she has of her father's creative use of language. She just remembered another beauty that is along the lines of the idiom, "When pigs fly." Following is part of an email she sent me:

"One (of the lines) he used to say when there was 'no way' he was going to do something was, 'Monkeys will emerge from my rectum.' It was hysterical! Especially the way he said it."

Thank you dear friend.