When you say them in public and people are just like what the heck are you talking about? And you laugh and feel bad not explaining but you don't want to explain because it's an INSIDE joke! Not and outside joke.
This is so my sister and I, people look at us like we are crazy! Which of course only makes us laugh harder! "My best friend and I are so hilarious. I feel bad for the people who don't get to listen to our conversations and enjoy the hilariousness.