There really was a Mrs. Yedvarb. She was our next-door neighbor on Avenue X in Brooklyn.
Yes, there really is an Avenue X in Brooklyn just as there is an Avenue Q. - for which the Broadway Show is named. The southern part of Brooklyn is divided into a rectilinear grid. The east/west streets are named Ave Q, R, S, T, U, V, W, X etc., and the north/south streets are named East 28th St, East 29th St., etc.