The material isn't that strange – Stone and Parker seem to enjoy working with puppets. But the flick apparently is shockingly clean. So clean that when all is said and done it'll get a G or PG rating.
Trey Parker and Matt Stone have already displayed their nostalgic fondness for Japanese giant monster movies as evidenced in the first season South Park episode, “Mecha-Streisand”. My only question is whether or not the intended audience (kids) will understand the jokes about the genre, especially considering that these kinds of films haven’t been shown on cable television in quite some time. I’m sure that the movie will still be pretty amusing regardless of whether the kiddies pick up on the satire or not, though.