During the montage of kisses, there is a scene recreating the famous (and controversial) moment on TV's 'All in the Family' when Sammy Davis, Jr. kissed Carol O'Connor on the cheek. This is appropriate since this kiss was scandalous for its time, just as Bart and Nicki's kiss was scandalous in this episode.
The producers of the show have never stated if Michelle Obama was asked to voice herself. Every President, Vice President and First Lady have been impersonated when appearing on the show.
If you look extremely close at the last scene, inside Nikki's locker and on top of it there is a symbol that belongs to the American rock band Linkin Park. This might indicate that Nikki is a fan of them.