Does anyone have a guest syndrome?

I am going to explain myself. You go to an event, that happens recurrently, and it's your first time going there. There are the usual organizers of an event, people who know each other since their high school or youth years or generally for a long time. They have built their own little inside world. They have inside jokes, memories, etc. (very normal stuff). They are probably kind and want to give you a welcome or offer something to eat. But deep down you know they are the owners, they know each other very well, and you are a guest. You go there repeatedly, still feeling like a guest because you don't have their experience inside the group and stuff.

Does it happen to you? Do you feel like you are always the guest, the brick of a decorative room's interior wall. Are you sensitive to exclusion?