One of the interesting topics that come up again and again is the diversity of German dialects - which, I once read somewhere, can be so far apart linguistically that they are actually different languages.
I grew up in Franconia, and thus know the Franconian dialect. Which sounds very, very different from what you can hear here, which is the Cologne dialect.
(And a really wonderful project, by the way! It's a song to get people to vote. There's original subtitles in German and Kölsch - and yes, they are quite necessary for some bits for Germans, too - but the automatic English translation is, unfortunately, quite shitty...)