Robyn and Yelle are best buds who are doing something called Foreign Exchange. This results in both of the ladies covering each others music and translating it into the language they originally sing in as well. It's pretty amazing. Yelle covered Robyn's "Who's That Girl" and put her crazy dance-pop-electro-glitzy twist to it.
Yelle - Qui Est Cette Fille?
Robyn - Who's That Girl?
Also, how many songs are called "Who's That Girl"? Seriously, just look it up on Youtube.