A pyramid scheme, by definition, is a business or financial program that uses the same money to make more money, with an emphasis on recruiting new members with promises of high returns.
PI (Puns In) Pyramid Schemes, on the other hand, use the same puns to make more puns, with an emphasis on making you laugh so hard you'll forget about the financial consequences.
Here are some pun-filled numbers to get you started:
4: The number of paws on a cat who's purr-fectly happy to be in a pun-filled number scheme!