When the Count is counting the end credits he says "Hi, Mom" when Joan Ganz Cooney's credit appears. Being the creator of the show and the founder of its production company, the Children's Television Workshop, she is sometimes referred to as the mother of Sesame Street.
The airline that Big Bird takes to Illinois is CTW - the abbreviation for Children's Television Workshop, the name at the time of the movie of Sesame Workshop, the production company behind Sesame Street.
When Big Bird is being welcomed home at the end of the movie; you get a quick glimpse of a character in a window that was definitively Elmo. The movie was made before he was even considered a character on the show.
The newscaster, played by Chevy Chase, opens his broadcast by quoting the theme song from Mister Rogers' Neighborhood (1968), another PBS kids' production which became popular during the same period as Sesame Street.