Invasion of the Tinfoil-Sect?

My colleagues and I like to have lunch at Café Weinwurm right on Stephansplatz. It's lovely to sit in the sun and just watch all sorts of interesting people pass by as you are waiting for your food. Recently, we saw a gang of people wrapped in scrunched up tinfoil. Hmmm. I just had time to quickly pull out my mobile and take a picture, just as the guy in front of me raised his hand to take a sip of his beer.
I don't think they were street performers (like those "statues" with gold or silver body paint), so there must have been some kind of fancy-dress party. Or perhaps this is what was left of Life Ball costumes after a night of partying.