I saw one yesterday that made me think of this thread, only instead of a shirt is was more along hte lines of please wear actual pants!
I was at Pizza Hut for lunch, and being on crutches at the moment (and their restaurant being so crammed with tables there was no way to maneuver around them) I was put at the table nearest the door and register. There were some men doing some repair work of some kind on the building and they came in for lunch. Now, I really could care less that they were a bit dirty and scuzzy looking- it's hot out there and they were working. However, one man had a huge hole in the back of his shorts that was right where his underwear was! He proceeded to stop at the register and chat with the waitress there (my waitress who never did stop by to refill my soda or do anything at my table. I had to get somebody else to refill my soda, closest I ever came to not leaving a tip). He butt was eye level with me, and everytime I looked up there was his underwear! My immediate thought was health department violation.
As he walked by my table, I politely said "excuse me sir, do you know that you have a hole in your shorts?" I know if it was me I wouldn't want to walk around all day with my underwear showing. He said something along the lines of "It don't matter. " I wanted to tell him yes it did matter! You are in a restaurant, I don't want your underwear hanging out, that is unsanitary! Yuck.