The last time a significant other and I shared a costume I was JFK Jr. and she was Carolyn Bessette. That was 1999. I was beaten by a guy who was Payne Stewart, complete with icicles on his golf cap. Brilliant.
Or wait, there was the year an SO and I were muslims. That was 2001.
lately it been guy-guy costumes, like last years Mark Foley to my Congressional Page.