I'm a big fan of Swedish Crime Fiction and recently I was lucky enough to come across this series (Der Kommissar und das Meer), loosely set on Mari Jungstedt's books, which was filmed in Swedish and German. Unfortunately one can only watch it wholly in either German or Swedish (it was filmed in both and dubbing is used over the conflicting language in each respective case). If both languages were utilised and subtitles were employed I think it would be my favourite series by far, not because of the story, but because of the mix of languages. Similarly, two Welsh productions that I saw recently mixed English/German (Resistance) and Spanish/Welsh (Patagonia) and they were both excellent stories and fun for polyglots. I have always found it hard to find a series to get into, but hopefully I will soon find more like this, where I seem to pick up vocabulary through context which means I am not only maintaining my language but actively encouraging it.