Pretty sure that's just a character Rainer is playing in a movie the Simpsons are watching in they're movie. We'll know for sure in a month.
There were some funny parts to this trailer. Mainly "Did I save the day?" "No, you doomed us all" and the Spiderpig bit at the end. Plus the animation was even better then what they showed in some of the previous trailers.
And for irreverent humor throughout. That is probably the weirdest MPAA reasoning I have seen since they rated the PPG movie PG for nonstop frenetic action violence.
Geez, the animation can't get any more gorgeous. That is some fine, smooth animations. That said, I'm still not raising any expectations till I see the movie, though I will forever be in Matt Groening's depth if they keep the Ralph Wiggum 20th century Fox opening.
I'm still not that excited. Especially because they're still going for the "parody of big budget summer movies" angle. South Park specifically already did the joke making fun of available technology vs the actual standard of animation.
My understanding is that movie studios are allowed to write their own listed "reasons" for the rating and have them approved by the MPAA ratings board. That's how movies have been rated R for "Extreme Partying" and such.