IDEA: Friendly Superheroes
Gradually introduce superhero nicknames for all your friends. Once the names have been somewhat established, change their names in your email addressbook to the superhero nicknames.
After a few weeks of emails they should all be used to this, whether or not they still think you're absolutely insane…
And that is when you send a mass email reminder to all of them about the next meeting of the Justice League.
It works best if you do this for people that don't regularly communicate with each other.