Who are these characters?

The other day whilst at comic-con I met to people dressed as two strange characters with a running theme. Both where carrying cylinder shaped things on their backs the guys one was blue and green and the girl had a silver one with what looked like a cake on the top. the guy had blue hair and white horns and the girl had blonde hair. I forgot to ask them what they where from and if you know please let me know hope that was enough info. Also they might not actually be from anime or even somthing they made up lol so it really doesn't matter if no one knows, just thought I'd ask. :S