This is not the first time we see Buffy's backyard. We have seen it in previous episodes from season 3, most notably in Dead Man's Party (1998) when Buffy and Joyce bury the zombie cat, and again later on when Oz steps out onto the porch. Plus, the yard is also seen in Real Me (2000) and Out of My Mind (2000) in season 5.
Pig Latin is a language game, that usually involves moving the first consonant of an English word to the end of the word, and adding "-ay" after it. For example, 'Buffy' becomes 'uffybay'. It has no connection to the Latin language.
A scene where the Scoobies are in the backyard was cut, when Anya says: "Why are you having us skulk around and meet in the backyard like conspiracy squirrels? Sitting on this arm is making my buttocks hurt".
Lisa Hoyle, who portrayed the hitchhiker demon, is a stunt woman who has done stunts for many films and TV shows. This includes: Charmed (1998-2006), Pearl Harbour (2001), Charlie's Angels (2000) and its sequel, the first two Pirates of the Caribbean films (2003, 2006), Iron Man 3 (2013), Once Upon a Time... in Hollywood (2019).
Spike says: "I overheard you and the Super Friends..". Super Friends was an American animated television series about a team of superheroes, which ran from 1973 to 1985. The core group of five heroes made up the "Super Friends" (and ironically Buffy, Willow, Tara, Xander and Anya also make 5).