Halloween costume ideas?!

I need an idea for a group of 4, for the same "theme". Maybe a TV show, movie...just something where there are 4 people. There needs to be two men and two women. The people dressing up are... My brother-in-law (husband's brother), sister-in-law (BIL's fiancee), my husband and I.

I feel like the whole post is chaotic, but I hope y'all can figure out what I mean.