Is This How Lenny Bruce Got Started?

My seven old son Alex invented this riddle last week: "What does a lady cat carry around? A purrrrrrse," and I thought it was quite clever-- though his delivery was atrocious-- but I assumed that although he "invented" it, that someone else had already thought of this previously, but I checked the all-knowing internet and did not discover its existence . . . so when I explain what a pun is to my students, I will use his example, and give him credit (I normally use the classic "what happens when you step on a grape? it lets out a little whine" as my example).