There is little doubt that San Junipero is one of the most beloved Black Mirror episodes for its bittersweet plot twist. However, Charlie Brooker has admitted that he was concerned about the truth being too obvious.
Brooker offered some interesting details about the episode in the book Inside Black Mirror (via Vulture). The creator confessed that he was worried that they had dropped too many hints about Yorkie's true situation in San Junipero.
"I thought we gave some huge clues, but people generally didn't pick up on them! There's a moment in Tucker's when the guy shows Yorkie this arcade driving game, and a car crashes on the screen. She has this horrible visceral reaction because it reminds her of the car crash that paralyzed her. Once you know what's going on, it makes perfect sense. We even put the noise of a car crash on the soundtrack, so I thought people would immediately go, 'Oh, she's been in a car crash in real life.' But no one ever picks up on it, until maybe a third viewing."
Brooker also pointed out the use of the Smiths song Girlfriend In A Coma "over a shot of Yorkie." The showrunner said he thought the viewers would quickly pick up on the hint but is still glad that it completely went over everybody's head.
San Junipero was directed by Owen Harris and starred Mackenzie Davis as Yorkie and Gugu Mbatha-Raw as Kelly. The episode is hailed as the rare Black Mirror episode with a somehow happy ending.