Wyndham from Wesley Wyndham-Pryce may be a reference to British science fiction author John Wyndham, the author of Day of the Triffids.

In Bad Girls, Mr. Trick says, “I like Marmaduke… nobody can tell Marmaduke what to do. That’s my kind of dog.” Marmaduke is a comic strip about a Great Dane who always gets into trouble. It’s written by Brad Anderson, and it began in 1954.

Faith tells Buffy in Bad Girls, “we can’t save the world in jail”. Faith is put into prison during Buffy’s fourth season for murder, and is broken out by Wesley in season four of Angel to help save the world.

Buffy fights with an Eliminati soldier in Bad Girls. He tries to drown her in sewer water. She says, “I hate it when they drown me”, a reference to her brief death in Prophecy Girl.

Faith steals a bow and arrow in Bad Girls, which she uses to shoot the courier in Choices, and Angel in Graduation Day (Part 1).

Giles’ first entry about Buffy into his Watcher’s Diary included the comments: “Slayer is wilful and insolent…her abuse of the English language is such that I understand only every other sentence.” His initial impression was probably made in Welcome to the Hellmouth. It’s read aloud by Wesley in Bad Girls.

Wesley gets a bad reception from the Scoobies when he first arrives in Bad Girls (”is he evil?”), because of the events with renegrade Watcher Gwendolyn Post in Revelations.

In Bad Girls, we discover the Mayor is going to have an Ascension in 100 days and that he is now invincible.

Balthazar’s last words to Buffy in Bad Girls warn her of the coming trouble with the Mayor: “When he rises, you’ll wish I’d killed you all.”

In Bad Girls, Faith asks Buffy if she has ever had sex with Xander, since they spend so many sweaty nights working side by side. Her curiosity is obviously sparked by the fact that she had sex with Xander in The Zeppo. Meanwhile, Xander’s eye twitches whenever Buffy mentions Faith.

The original pitch for the character of Wesley was for him to be a bit like Michael J. Fox in Back to the Future (wiry, enthusiastic etc), and so to get on Giles’ nerves in that way. The writers eventually decided to try and make Giles look cooler and rebellious …

Willow refers to herself as a Wicca for the first time, as opposed to a witch, in Bad Girls.

Sarah Michelle Gellar showed the names of every person that worked on Buffy at a 1999 Tonight Show appearance because she told them that if she mentioned them on the tonight show that they’d have to go see her latest film Cruel Intentions.

Christian Clemenson, who played Balthazar in Bad Girls, has also been in the movies Mighty Joe Young, Armageddon, The Big Lebowski, Apollo 13 and Hannah and Her Sisters. He has been in many TV shows including NYPD Blue, The West Wing, Mad About You, Lois & Clark: The New Adventures …

Xander runs through the list of colleges Willow has applied to in Bad Girls. One of them is Wesleyan College in Connecticut, which is also Joss Whedon’s Alma Mater.