[tortoise]

Many a penny has been found among the dung.

Working minimum wage would be more rewarding than digging through turds for pennies. I would wonder about the "good fortune" of finding a penny in a pile of manure. (Yes, I know. Metaphor.)

Sounds like a game show idea that Fox would buy into...

[Old Professer]

It wasn't a simple metaphor; it was a silly wordplay; let it roll off the tongue, so to speak.