I had a crazy moment this week: I was curious about Yiddish and pulled up some lessons. I almost fell off my chair when I could understand a good deal of it. Sure, I imagine that you, the reader, are rolling your eyes as it might be common knowledge that it is strongly influenced by German. However, where I come from, there aren't a lot of Jewish people and my overview of linguistics during college was very basic so while I knew it had European influences, I didn't realize how Germanic it was.
I was quite pleased that I could understand it. All this work I'm putting into learning German is yielding even more knowledge than what I had imagined it would :)