When Mr. Popper realizes the expense of housing the penguins, what idea does he come up with to make extra money in the novel, Mr. Popper’s Penguins?

When Mr. Popper realizes the expense of housing the penguins, he decides to stage a show. The Poppers train the penguins, coming up with a three-act show: marching, a "boxing match" starring two penguins, and climbing (and then sliding down) ladders. The Poppers take their penguins to a local theater, where the owner, Mr. Greenbaum, loves the act and decides to hire them for a nationwide tour.