Cultship

A cultship is when a group of friends bond is so strong that they become their own cult, and can only be achieved after a group of friends have established numerous inside jokes. After this is achieved, the group's friendship will evolve into a cultship.

Debra: Wow, I wish I had your group's level of friendship.
Jack: Woah woah woah, a friendship wouldn't laugh at potato's and cows cause of an old joke. We're a cultship.