When the BSC are posing for a photo together at the end of the episode, they are arranged in the same order that the characters were for the cover art in the corresponding book - "Baby-Sitters' Summer Vacation"- published in 1989.
At 6 minutes 9 seconds, after Kristy says "Put on your tick spray--we're going into the woods.", Mallory starts singing "Into the woods and out of the woods and home before..." at which point Kristy cuts her off. This is a lyric by Stephen Sondheim from his 1986 musical "Into The Woods" which was made into a movie in 2014. Specifically, the lyric is from the last lines of the song "Prologue" which opens the play and film.