I have to go with Disharmony, because there were so many funny moments. Harmony popping her chewing gum, and when Wesley gets annoyed about it, she tears out a page from a book and spits the gum into it.
Wesley: "What are you doing?! That book is twelve centuries old!"
Harmony: "Okay. Well, it's not like I messed up a new one."
Also, the gang giving Angel such a hard time as he's attempting to work for them is hilarious. Especially giving him that tiny place to work. And giving him their orders for coffee. And Cordelia initially thinking that Harmony was, "...a great big lesbo." 😅
And you have to admit, a vampire motivational speaker is pretty amusing.