Sometimes there are strange things going on in San Francisco and it happens every May.
It is an event called the How-Weird Street Fair, aptly named so after Howard Street, for that is where most of it occurs...
I went there in 2014 and shot the photos you can see below.
To see larger versions of the pictures, click inside of any small one. Some may be too large for your screen, in which case you have to scroll down to see it all.
You can also right-click in the expanded view and have Windows define the appropriate size.