From the man himself:

not photoshopped...it was years ago...some wild eyed guy was blurting out questions at a Shoreline Amphitheater concert and he asked if I went to the urinal on my Segway. What would you say? I answered "yes." Always say "yes" when someone is excited with a weird or impossible question. Then this guy asked how I did it. I was stalling to think of some funny reply when he asked if I stood on it backwards and held the handlebar so I said "yes" again.

Then I went into the urinal and set up the photo with friends. I posted it myself on urinal.net.

Later that night I showed the photo to a friend and told him how I turned the Seway backwards because of splash from the Segway stick. I then rubbed the stick and commented that it was still a bit sticky and asked him to rub it too but he would have nothing to do with that.

It was a fun evening!