Sarah's MJ is there, although she's off in the corner. She somehow found a Wonder Woman costume and wears it a little more modestly than in the picture (mostly a longer skirt). - Gets dragged into the possible Thriller sing/dance off and is an awesome singer, thank you very much. Less so an awesome dancer. Possibly also gets stuck in a flying pumpkin if anybody wants to :D
Loki is Captain America for the night. He doesn't need any fancy drinks or cakes to fake acting Patriotic and Righteous, although he does end up eating a strawberry and ends up as Ghost Captain America.
Tony embraces the character archetype of a genius tech billionaire and goes as Batman. He's gonna have one of the Vampire Shots, so go mad.
Newt is dressed as a very stereotypical vampire, but he's gone all out on the blood and brought along Pickett, who doesn't have a costume but does have a penchant for making faces over Newt's shoulder.
Jim Kirk is going as a different kind of captain and becoming a pirate, complete with makeup.