This was Jim Henson's final performance as Kermit the Frog (as well as Ernie and other characters) in a theatrical feature.
When the Count is counting the end credits he says "Hi, Mom" when Joan Ganz Cooney's name appears. She is the creator of Sesamstraße (1969) and the founder of its production company, the Children's Television Workshop. She is sometimes referred to as the mother of 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 airline that Big Bird takes to Illinois is CTW - this refers to Children's Television Workshop, the name of the production company behind Sesame Street (it has since been renamed Sesame Workshop). The flight number is 1138, possibly a reference to the George Lucas film THX 1138 (1971).