The MPAA's a little funny like that.
NC-17 pretty much restricted to pornographic torture-porn and not much else
R-Rated - parents can bring you to 'em
PG-13 - We'd really like it if parents brought you, but well we're not really going to pay attention if they don't because we only 'suggest' parental guidance
PG - similar to PG-13, we suggest that you take yer kids to see it.
G - Disney. Yay.
http://www.mpaa.org/FlmRat_Ratings.asp
