In season two, the line "what are you doing here?" or a variation "what am I doing here?" is said at least once per episode.
Amy Sedaris hated doing the tongue-twisters, so the writers responded by giving her the most of any cast member.
Will Arnett named BoJack as the hardest role of his career to get inside, admitting that he sometimes took the darkness of the character home with him.
Margo Martindale didn't immediately know that the world of the show was populated by humanoid animals as well as humans; after her first recording, she told Will Arnett how much fun she had in her session, and that Mr. Peanutbutter had oddly dog-like qualities.
Rare for an animated series, there is a table read before every episode, allowing the actors and actresses to interact with each other.