Some of these are narrators, some are interlocutors.
A narrator moves the plot along or comments on it without directly participating in it. An interlocutor is the go-between for the world of the show and the world of the audience.
The Narrator in Joseph is a narrator, as is Old Belle Poitrine in the original version of "Little Me" and the Criminologist in Rocky Horror. Mark Cohen in Rent is an interlocutor, as is Sue Snell in Carrie.