What does "number one at number two" mean? In what circumstances could I use it?

Native speaker’s answer
Rebecca
Ah, this is a funny sentence with a bit of wordplay! So, "being number one" refers to being the best at something here, and "number two" refers to excreting feces. I guess 'cause she's a nurse, she has to help patients in many areas, including going to the bathroom. It's like an indirect and softer way to say that you need the bathroom for a certain purpose. Ex: You're number one at submitting your reports on time. = You're the best at submitting your reports on time. Ex: I'd hate it if I were camping and needed to go number two with no bathrooms around.