When Big Bill shows Little Bill the envelopes so he can see the address, none of them have a city, state, or zip code listed, and the return address only has the sender's name instead of a full address.
Monty is shown to be a member of Little Bill's class, even though the episode "Monty Joins The Class" airs after this one.
Little Bill: (singing and dancing) I got a letter! Boom! I got a letter! I got a letter! Ooh! I got a letter.
Big Bill: Aren't you going to open it?
Little Bill: Oh yeah...
Little Bill: I'm going to learn how to read books and show Bobby!
Alice the Great: I'm right behind you. Let's go.
Viewers learn Andrew's last name is Mulligan.