MS Paint Adventures is a weird comic and/or a messed-up game, depending on how you look at it. It's a comic, done in the style of an old adventure game, created as a collaborative effort in which the main character's actions were based directly from the readers' suggestions and queries. The fourth wall is rarely broken except to poke fun at the readers and some of the really dumb suggestions.
I'd guess the whole thing falls under PG-13 for occasional mild swearing and innuendo. But I'm not sure how mature a cartoon has to be rated to have swear words in it.