The itty-bitty penis bit

[Author's Note] O.K. this is my first post and honestly I have no idea how to write a joke so I am just probably going to use a topic of conversation that I bring up all the time. Mostly, I use this to initiate conversation with people and is fallback topic I use in conversation.  

Usually, I just riff on this topic and like to see where it goes but I'm trying to imagine this in a stand up scenario so I've tried to write a more cohesive style of joke that I could maybe talk to an audience about.