In the Swedish/Danish TV series Bron/Broen (aka "The Bridge"), when Saga (from Sweden) and Martin (from Denmark) are together, what language do they speak? How about other characters? We don't speak either language and watch with English subtitles so we have no way of telling for sure.
They both speak their native language. Saga speaks Swedish and Martin Danish.
I have no idea about the other characters as I haven't seen anything of the show myself, except for trailers, but they are most likely speaking their native language. So, whoever you can identify as a Swede would most certainly be speaking Swedish, and all the Danes would most likely be speaking Danish. We Swedes do have a bit of a hard time understanding Danish, though, so don't be surprised if they start speaking English all of a sudden ;)