If I was clever, I'd figure out how to filter a dictionary of standard English words down to those that could be spelled by reading correctly oriented letters upside-down.
If I was really clever, I'd figure out if there was a word to describe this kind of graphic presentation, or make one up. I think it might be classified as a type of natural ambigram.
But I'm neither, so I'll just sit here and look at the arbitrary perfection of this one. I mean, "umop-ap!sdn" spells "upside-down," upside-down.
That's just neat.