You ever notice how the chorus of Material Girl is a 7-bar figure, so when later in the song it repeats after 8 bars, it gives this INCREDIBLE jumpy feeling of skipping back to the best part so soon???
the main reason it sounds surprising is because the vamp guitar riff starts and gets cut short after 1 bar when it normally expresses itself in 2. you could do the chorus in 8 bars and just land on that 1 chord for bar 8 and go back around without the guitar vamp riff, and it would sound totally expected. but because the vamp riff starts and does not finish, that is what seems to give it the surprising quality