The fourth season of BoJack Horseman is the darkest yet, but that doesn't mean that it's not entertaining or funny. The show's strength lies in the way it combines the three, the outcome of the mix being one of the best series airing right now. It handles throwaway jokes and elaborate, season-long plot developments with the same gusto, exhibiting great respect for the viewer, who feels rewarded for the time invested in watching.
There's rarely a moment of dullness, and the writing is never half-hearted. The show is full of great, gripping moments. Some of them are instant, almost spontaneous, and require no preparation on the part of the viewer, while others take a whole season to reveal, and some time to actually 'get'. That's why the show is so watchable and interesting to analyze.
This list clearly doesn't include all of the eye-raising moments taking place during the season, since one episode of BoJack Horseman is ideally a string of these, one happening after another. Instead, it focuses on the key and unique ones, which really make BoJack, well, BoJack, and when there was plenty of Horsin' around.