BoJack originally let Todd stay at his house because he thought he was a troubled gay teenager, probably to make up for selling out his best friend who was blacklisted for being openly gay.
We also find out that the Halloween party that Todd stayed after was the same night Bojack found out about his father's death. Todd is clearly concerned for Bojack even though he had never met the guy before.
In "Later," Mr. Peanutbutter reveals that his Anti-Nihilist personality is a result of him just distracting himself from the harsh realities of life until he's dead, which Diane thinks is the reason he doesn't want her to leave for Cordova. In "After the Party," he tells her that he doesn't want her to go because he's terrified of losing her, and wants nothing more than for both of them to be happy until death do they part.
Mr. Peanutbutter: Okay, you got me! Maybe I don't want my wife - whom I love - to go off on a terrifying six month tour of the most war-torn, disease sputtered corners of the planet, with a charming, handsome billionaire bachelor!? What could I be thinking??? I'm such a terrible husband!!!
"After The Party"
Mr. Peanutbutter dedicates a room to Starbucks; in "The BoJack Horseman Show" it's revealed that he first met Diane when she was working in a Starbucks.
Princess Carolyn breaks up with Vincent in this episode when she "finds out" that he has a son named Kevin, whom Vincent claims that she never met because he was worried about how she would react to marrying a divorced father. What's more, Princess Carolyn asserts that Vincent is obviously lying to her and hiding something; she says that she wants something more than a person who is nice to her on the surface but has nothing underneath. Princess Carolyn badly wants to start a family, and she wants a partner whom she can trust. The series ends with her receiving both after she adopts a baby named Ruthie, and marries her Hypercompetent Sidekick Judah.
The Season 3 finale reveals why Diane is able to put up with BoJack - Horsin' Around is what helped her make it to adulthood while putting up with her awful family. If not for that half-hour a week of Glurge, she may very well not have made it.
In "The Shot", Mr. Peanutbutter explains his character on Mr. Peanutbutter's House left the office of US president because he doesn't want it to distract him from his family. In Season 4, Mr. Peanutbutter stops running for governor because Diane helps him realize he isn't really fit for the position, and because it's better for their relationship for him to stop and have down time with her.
Season 2 ends with the jogger telling BoJack "Every day, it gets easier, but you gotta do it every day. That's the hard part." The next seasons would prove to be the show's darkest, ending with BoJack losing almost all of his friends and inadvertently killing one. However, the season after that showed him finally develop into a nicer person, even regain several of his friendships as a result and even welcome a new one into his life. He got past the hard part.
Season 4's "Ruthie" reveals that Princess Carolyn's treasured family heirloom was a simple piece of costume jewelry, which is depressing. What's uplifting, though, is that she was from a family of 9 children, and this means that either her mother or father still cared enough about her to give her both the necklace and the inspirational lie to begin with.
Season 5 reveals it was her mother that told her the lie, just after P.C. had learned she had gotten pregnant by Cooper and was in serious need of support.
Just two years after the show's vicious attack on the machine that enables sexual predators in positions of power in "Hank After Dark," the New Yorker's report on Harvey Weinstein's long history of sexual assault opened the floodgates to all kinds of victims coming forward and being taken seriously, and the abusers quickly losing much of their support.
Bojack and Diane's friendship, flawed as it may be, becomes this when we actually see their first interaction in "Mr. Peanutbutter's Boos".
Similarly, for those worried that Diane claiming to have been a fan of Horsin' Around in Season 4 was a Motivational Lie, that episode dispelled the idea entirely, as she made it clear that the show was what kept her going through her childhood.
Gina's growing success because of her role in Philbert could be this because at the same time, Rami Malek who voiced the creator of the show Flip McVicker was also gaining a lot of popularity after his portrayal of Freddie Mercury in Bohemian Rhapsody. The similarities between these two are that they both started off their careers playing supporting/one-bit characters and later received a lot of recognition and popularity in their mid to late 30s.
In a more bittersweet example, at the end of Season 3, Bojack laments that he has nothing to show for the life that he's lived, and that nobody seems to be better off having known him. At the end of the show, Diane and Bojack share one final heart to heart talk, and she says she's glad she knew him. While it's sweet, she also emphasizes the past tense of knew. She's left behind her life in Los Angeles completely and gets on with her life in Houston, so as much as Bojack doesn't want it to be, that conversation is likely the last the two will ever have.
On the flip side, Diane wanted to make a difference in the world with her pen and good intentions. BoJack starts to get out of his depressive rut when Diane starts writing about his life, and it's clear despite their ups and downs, she was a good friend to him which was what he needed. To a lesser extent, she ends up writing a book series that changes the world by making people happy: Princess Carolyn loves Ivy Tran and wants to share it with her daughter, while Guy's son bonds with Diane over it. She didn't save women from sexual abuse, but she brought joy to her friends and family.
