I did the Cleveland Critical Mass October ride. It was a lot of fun, felt like being in a parade. For the most part pedestrians and motorists took part in the fun, waving, cheering and giving friendly honks.
This couldn't be comfortable to ride in. Very funny though:
My favorite costume was the Venture brothers Henchman:
This was my favorite bike, apparently it was sold by Rivendell.
Double Decker ghost bike:
Tower city on public square:
Super cool low-rider: