Yeah, I know, i know ...it is pretty funny watching a bird fly into a window or glass door and knock itself out.
But I was leaving a party on the weekend and mistook a plate glass panel next to an open door for the open door and I tried walking through the glass panel that I thought was the open door, but it wasn't an open door, it was a plate glass window thing.
And I then realized that the only thing that hurts worse than full-on headbutting a plate glass window is the sting of the laughter of those who heard the crunch and witnessed you bounce off of what you thought was an open door.

And the only thing less funny than that was that I was carrying a baby in my arms at the time.

Still, probably wasn't as bad as that time my friend had her nose severed running through a ranchslider door. For the record, I don't advise doing that either.