To take advantage of a friend with a higher income so that they will pay your way for lunch, movie tickets, etc. This can either be with prior notification (notifying the friend that they are about to be the recipient of this action) or it can be a surprise poodling, such as when you seem to have forgotten your wallet when the bill arrives.
Having to take a dump so badly that the turd is starting to wiggle its way out of the gate. Incorrectly defined on urbandictionary.com as turtle head, "turtle tail" is a much better descriptor for a tapered turd that has quietly poked its way out of your posterior.
Dude, can you pull over at that gas station? I've got a turtle tail.