My dad tried to teach me how to invest.

The humor in this joke springs from a delightful bit of wordplay, taking a common phrase and twisting it into something hilariously literal. When the dad advises putting money into a "piggy bank" as an investment strategy, we initially think of the ceramic or plastic coin holder that's a staple of childhood savings, a simple way to stash away a few bucks.

However, the punchline flips this on its head, revealing that the joke is imagining a *literal* bank that houses a *literal* pig being fed money. The absurdity of a financial institution intervening to stop someone from "feeding" a live animal with cash is where the big laugh comes in. It's a clever subversion of expectations, playing on the dual meaning of "piggy bank" to create a wonderfully silly image.

This joke also lightly pokes fun at the vast difference between sophisticated financial investing and the simple act of saving coins in a child's piggy bank. While a piggy bank is indeed an early lesson in saving, a precursor to more complex financial literacy, it's a far cry from the world of market investments. The humor comes from the dad's well-meaning, if comically misguided, attempt to bridge that gap with a literal interpretation.