I did an internship there ages ago (10+ years), in the Munich office, so my experience is probably of little help. But for some reason, I remember the interview relatively vivid.
I had three interviews, besides the general CV chit chat I had one market sizing case (number of Panini stickers and albums being sold in Munich - this was shortly before the World Championship in Germany in 2006). There were also quite a few relatively serious questions (considering that I was a student, coming in for an internship) about marketing and brand. I remember one case about the "awareness funnel" in marketing and one question about functions of a brand.
Hope that helps (a little bit at least),