Princess Carolyn dresses up as Amelia Earhart every Halloween at BoJack's party, which is properly set up in The Amelia Earhart Story (2018) by how she would watch Amelia Earhart on television throughout her childhood.
When Mr. Peanutbutter talks to Pickles about Diane, the two spring breakers who try to rob BoJack's car in The Telescope (2014) pop their heads out of BoJack's front door.
In the 2018 party, a party-going fox in the background is dressed as Zoya the Destroyer from GLOW (2017), who is played by Alison Brie. She also voices Diane Ngyuen.
A background character in the 2018 party is dressed as Steve Harrington from Stranger Things. Specifically, he is wearing Steve's outfit from season two and carrying around a baseball bat with nails in it. Stranger Things and Bojack Horseman are both Netflix Original Series.
In the 1993 party, there is a piece of art on the wall of Bojack's house - reminiscent of the work of the famous artist Keith Haring.