- Irony as She Is Cast: Kelly says something mocking England when Yorkie uses the word "deflowered", Kelly's actress (Gugu Mbatha Raw) is English (and an honored Member of the Most Excellent Order of the British Empire, at that- though to be fair that happened AFTER the episode was filmed).
- Quote Source: For Artificial Afterlife.
- Separated-at-Birth Casting: In "San Junipero," Denise Burse (elder Kelly) looks like she could have been Gugu Mbatha-Raw (younger Kelly) under aging makeup. Their 31-year age difference suggests they could quite convincingly play mother and daughter.
- Very Loosely Based on a True Story: Brooker's inspiration for the episode was an experiment done where elderly people were put into a simulated environment evoking the period of their youth that showed they became much livelier and physically able, which he'd watched a documentary about in 2010.
- What Could Have Been:
- Originally, San Junipero was supposed to be about a heterosexual couple, but Brooker found that switching it to a homosexual one immediately made it more interesting. Early drafts also did not include the happy ending.
- There was going to be a kindergarten with dead children, but the idea was abandoned because it was too sad.
- Charlie Brooker and co. originally wanted Mackenzie Davis to read for the role of KELLY- but after reading the script she asked if she could play Yorkie instead, since she had already played lots of Kelly-esque characters whereas Yorkie would be something new for her.
- According to the behind-the-scenes book Inside Black Mirror, Charlie and co. briefly considered having Gugu Mbatha-Raw play both the young and old versions of her character (Kelly) by having her don old-age make-up and/or prosthetics for the latter (something that Mbatha-Raw says she was totally game for!). But they ultimately decided against it, concerned that they wouldn't be able to make the transition believable enough.
Trivia / Black Mirror: San Junipero