re: Black Mirror S3 has dropped on Netflix

I have noticed some of the episodes contain callbacks or references to other episodes - implying all the stories are in the same universe.

I noticed the song from "15 Million Merits" was in "White Christmas" and in "Men Against Fire" (soldier one from season three).

I also noticed in "Hated in the Nation" that Blue (the tech detective) mentions she left forensics because of the "Ian Rannoch case" - Ian Rannoch was the boyfriend of Victoria Skillane - the main character from "White Bear".

Also, one of the symbols on the table that turns into Whack-A-Mole in "Playtest" is the same symbol from "White Bear".

Not surprisingly, someone on Reddit has listed all the connections here.

I hope one day - maybe the series finale? - we get one overarching story that ties it all together.