In S02E04 of Riverdale, “The Town That Dreaded Sundown,” the serial killer is on the loose and Jughead goes to the public library to get some books on the subject. The library is a traditional TV show library, and the librarian is the stereotypical prim grey-haired woman. However, there’s a twist: her name is Mrs. Paroo. She’s named after Marion Paroo, “Marian the Librarian,” from The Music Man, which was set in River City.
Later Betty goes to the library to get some books on ciphers and cryptograms, but we don’t see Mrs. Paroo, perhaps because the library seems to be closed. How they got in, I don’t know, but the kids seem to be able to get into any building they want.
My theory about Riverdale is that it’s actually a soap opera set inside the Archie universe. There are a number of stories in the original comics where actors come to Riverdale and play characters based on Archie, Veronica and Betty. (This always leads to hilarity and confusion.) Riverdale is one of them—it exists inside the Archie universe—and I think Archie and the others are watching the show in confused amazement.