What is up with Ricken’s friends?

I just rewatched the Season 1 finale and everyone Mark interacts with at Ricken’s book party is SO strange. First Rebeck with the sores from her bird, small eyes and overall weird demeanor. Then the friend (idk if he has a name or not) from the dinnerless dinner party makes the comment about if baby Eleanor should have made her debut at the party (rude but whatever) and then when Mark S. And everyone are looking for the baby and they find her in a room the friend screams some weird shit like I HAVE FOUND YOUR BABY - when Mark S. Was the one who opened the door…. I’m sure this has been discussed before but are there any theories on this???