Mamdani's political strategist wrote a book

[Syne]

Morris Katz did write a line in the book, Everything You Always Wanted to Know About Puberty—and Shouldn't Be Googling: For Curious Boys, stating that he originally wanted to use images of his own penis to explain anatomy. However, the publisher rejected the idea, so no such photos were actually included in the final book.
Context of the Remark
The text within the book explicitly notes the rejection as a meta-joke or commentary. Katz wrote:

"At first, we were going to use images of my penis to get this point across, but the publisher said it was inappropriate, so here we are."

Instead of actual photographs, the final published book utilizes stylized, non-explicit illustrations and a basic line drawing to demonstrate anatomical changes.
- gemini

He wanted to show his penis to young boys.