In search of Medium Foot

It is really quite cold in Wisconsin in January.  So when we were out for a walk recently we were surprised to see this:

We followed the tracks for a couple of blocks before we lost them.  Quite a few of the foot prints had that odd drag mark in back of the heel.  What was a barefoot shuffling person doing out on such a frosty day?  Or was this track made by something like this?

I guess this was a fashion fad that I had missed.  Just as well, I think these are creepy.