This is turning out pretty long. Some day, I’d like to systematically go through the show and jot down all of these details, but that would take a long time.

The flatline is an interesting detail: At the end of 15, we hear it, then the beep resumes. But at the beginning of 16, we see BoJack and Diane sitting on the roof, looking up, and then the beep comes back in, increases, and flatlines again. I believe this is when he actually dies. The show does a lot of misdirects - a couple innocuous ones from S1 are the birds having blackmail on BoJack that never amounts to anything, and Todd never finding the BeastBuy receipt that shows BoJack sabotaged his rock opera - and I believe the transition to Horsin’ Around is one such misdirect.

When BoJack is on his bender in S1E11, we see a lot of surreal references to impactful moments or conversations in his life, like his dad forgetting to pick him up after a soccer game, him sinking into a tar pit like Charlotte talked about, and he and Herb fighting and then Herb dying. I believe we see the same memory bleeding in 16 with his guilt over killing Sarah Lynn, which means BoJack is not experiencing actual events: PB reveals the Hollywoob sign at the planetarium even though we have never seen the Hollywoo(d) sign and the planetarium in the same shot (I believe, although I would have to watch the entire show again to verify this); when Todd brings BoJack to the beach to watch fireworks, we keep seeing flashes of red and blue on their faces, just like the lights from the police car at the planetarium when BoJack waits 17 minutes and then calls for help (there is also some yellow from the ambulance); and when each of the main characters stops talking to BoJack, we get a brief blackout transition before the next character starts talking, just like BoJack keeps blacking out during the S3E11 bender episode. We also learn about the BoJeebies kid who found him in the pool, and it looks like he’s falling into a life of predatory fame. BoJack freaked out when Olivia said she wanted to be like him, and I think he worries that he’s going to ruin someone else’s life just like he ruined Sarah Lynn’s.

In the car, BoJack has a line where he tells PB he doesn’t want to go to the wedding because he thinks that something bad is going to happen. He also looks suspiciously at the sign for the roof before PC starts talking to him, and this sounds like a premonition of his death, as in “Once I say goodbye to Diane, I have no reason to hold on.” In a similar vein, PC has a strange line where she says she that Horny Unicorn is doing well and he could get back into acting, then backtracks with “I’m sorry I said anything”; this sounds like exactly the kind of fumbling statement you’d say to a dying friend before you realize quite what you’ve said.

I will say none of this is ironclad and I could be wrong, and I like that such finely-tuned details exist. One thing I know is that we know BoJack couldn’t have actually died at the end of 15 because he would have no idea that PC and Diane married, which we got independent confirmation of earlier on, so I think that everyone saying farewell to him in the hospital while he’s in a coma, or at least some drugged-out state.