go as (someone or something)
To attend a party or other social gathering in costume or dressed up to resemble someone or something. I'm going as Marilyn Monroe—how about you? A: "We should go as fairies!" B: "Yes! I already have a pair of sparkly wings from an old Halloween costume."
go as someone or something
to pretend to be someone or a type of person. There's a costume party this weekend. I'm going as Santa Claus. My husband and I are going as a king and queen.