favor for brother

Took L to New York to have a voice lesson with P.  Afterward we met his girlfriend (E) for pizza.  P and I told the old standard "cute little brother" story about the time L had been playing starwars with P...
Wow - come to think of it -  L learned how to talk early.  We lived in a specific apartment for 1 year which is why I can place his age so well.  We always say L was three years old when this story happened, and he may have been, but he was barely three.  We moved out of this apartment in July and P left for his summer trip in June.... So, I can fix pretty exactly the latest date in which this exchange could have happened.
The anecdote goes that L and P were playing Starwars and at a certain point L delivered the key line from the fight scene between Skywalker and Vader, "Luke, I am your papa."  At least that was this adorable 2-3 year old's version of this dialogue. 
The point of this story is that we were joking about how we always tell this story because it's just too cute and L said something about how we tell it to "all of P's girlfriends."  Ha ha.  L is oblivious, but I think I detect a micro-expression flit across the face of current girlfriend.  Sigh... I said, "We tell that anecdote to everyone who comes into our lives."
In the metro station, as we head toward home, I told L he could do his brother a big favor by never saying things like, "We tell that story to ALL of his girlfriends."  He was painfully cute because the sudden understanding on his face was so evident.  I said not to worry, that unless P and E broke up that very day there was no harm done (God forbid).... but for the future...