When I attend MNSSHP, the weather is super hot. I usually wear clothes I already own and just wear something on my head as a costume. Cat ears, devil's horns etc.
This is what we wore in 2012, my last visit. I have to admit that it was a warm night, and the vest and long sleeve shirt got me sweating. One year we went and was trying to stay warm.
When we went in 2010 we dressed as characters from the sword in the stone. I was madam mim, hubby was Merlin and my (at the time only) son was Wart. We were going to go in 2012 with some family and had plans to go as toy story characters with my oldest son as Zurg, my cousins child as Buzz, my now 2 year old as an alien, my hubby as Woody, me as bo peep, my daughter as Barbie and my cousin as Jessie. Now there are two additional babies (one from me and one from my cousin) so if were to try that next year I would have to really figure something out. That is a ton of people!