I was in a bathroom stall yesterday minding (and doing) my own business....when a father and son entered the bathroom. I'm going on voices only, so this is only my assumption of course, but I'm pretty sure I'm correct.
Dad: Why don't you go in there.
(son enters stall next to me)
Son: Hey, someone wrote on the walls in here.
Dad: (laughs) It's a good thing you can't read yet.
Son: It says - 'D.I..."
Blobby: (starts chuckling)
Dad: (chuckling). Ok! Ok! That's enough.
...as for the attached image? I snapped that in a resturant bathroom a few weeks back. I don't get it. Gooooogling only made it that much more confusing. Anyone care to clarify?