Halloween Costumes

Three day weekends are so much fun. On three day weekends I get to hang out with my friends and family. There is a three day weekend this week because it is Columbus Day on Monday.
Saturday night I went to a Halloween store called Spirit with my best friend, my mom, and my brother. My friend and I were looking for group Halloween costumes. The reason being six other girls and I are going trick-or-treating together. We all want to wear matching costumes or the same themed costumes. When I was at Spirit with my friend we saw super hero costumes that were super cute. There was Robin, Batman, Wonder Woman, Iron Man, Captain America, Spiderman, and superman.
We had before thought about being minions from despicable me but not everyone was happy about that idea (I wasn’t in love with it myself). So we abandoned that idea. I think super heroes would be a good idea. At the moment only one of the six girls knows about the idea I will probably tell the other five on Tuesday at school. I really want to do something as a group and I hope none of the girls give up on trying to figure something out. Does anyone have any ideas about what seven girls can wear as a group for Halloween?