1.The show's theme song was never intended to go anywhere or be on the show – it was recorded by Black Key's drummer, Patrick Carney, just to test out the his equipment at his home studio.
2.The opening credits change to match the theme of each season – in Season 2 the background includes the set of Secretariat, in Season 3 it includes the red carpet for the movie premiere.
3.In season 4 each episode's opening credits change to reflect the nature of his relationships at that point in time.
4.The show's creator Raphael Bob-Waksberg and production designer Lisa Hanawalt have been friends since high school and they'd often joke about what their TV show would look like if they had one.
5.They've designed characters based on their former high-school classmates.
6.Unlike most animated shows, there is a table read for every episode, allowing the actors to interact with each other.
7.The inspiration for the show came from the drawings of animal heads on human bodies Hanawalt had been doing for years.
8.When real-life public figures are written on the show, they are usually asked to voice their fictionalized characters.
9.If a celebrity is offered to voice themselves and they say no, their namesake will often end up being rewritten to be a little meaner than if they'd say yes, or they'll suffer a cruel fate.
10.The change in the tone midway through the first season was so drastic, it resulted in IndieWire changing its policy to only review entire seasons of shows on Netflix for a fairer rating.
11.Will Arnett has admitted that because BoJack is often so dark, it has been the hardest role of his career to get inside.
12.Netflix created a 90s themed acting website for BoJack, which even autoplays the Horsin' Around theme song.
13.The Zoe or Zelda dichotomy is based on an observation the creator had about Tia and Tamera's opposite personalities on Sister, Sister and how you can assign your friends to ~being~ one or the other.
14.Daniel Radcliffe was not originally written into the script, the character at the time was just written as "Major Celebrity". Radcliffe ended up getting the role because he's a huge fan of the show.
15.It was decided early on that all animals on the show would be animal-people and no one would have pets. Until a joke about a cow waitress serving steak was written, there was supposed to be a no meat-eating rule, too.
16.The characters' clothes are deliberately chosen to define their personality, and some outfits are inspired by things celebrities have worn in real life.
17.While pitching BoJack Horseman, Bob-Waksberg was told there were already too many shows about Hollywood, and people were sick of them, so he rewrote it as a pitch for a show about a washed-up racehorse.