In most of the places that celebrate, the idea is that women take over everything for the day. So usually in those places, at 11.11am on the Thursday before Shrove Tuesday (it is all related to Easter and Karneval) women dressed as old crones, storm the town hall, cut off the Mayor's tie and then take over all the offices. In reality they now just dress in fancy dress, storm the building and everyone eats doughnuts and gets wazzocked.
It is my favourite day of the year to go to work on the train because it is EXACTLY the same as always, dark, cold and the usual groups standing around looking tired, grumpy, having a smoke, scrolling on their phones, briefcase by their feet. But there will be groups of people dressed like cows, Sailors, Penguins, doctors... anything. But just behaving totally normally because Altweiber actually starts at 11:11 and not a second before.