Some people have alleged that it is offensive to Muslims. Strip artist Johnny Hart denies it. I agree with him, although I think it's a pretty generic strip. Many of his have been a lot funnier than just bathroom humor.
Anyway, the accusers say that his repetitive theme of the crescent moon shows that he's talking about Islam. But if he used a circle for the moon, some might be confused and think it was the sun and, therefore, think it was daytime. And he has the crescent moon on the outhouse. But aren't most outhouses depicted with a crescent moon?
The more subliminal poke at Islam is the world "SLAM" spelled vertically instead of horizontally within a space that looks like a large white letter "I" so put it all together and you've got "Islam."
November 10th was the 15th day of Ramadan, pretty much right in the middle of their holy month. Good call on that, Stephanie!
