When Keith is singing his new song that he came up with there are two different voices. During the filming of the episode the producers found out that David Cassidy could sing so in part of the song it's someone from the studio and then changed to David before going back. Later episodes David Cassidy would sing the songs.
Not only is the song "Oklahoma" mentioned, its composers "Rodgers and Hammerstein" are mentioned twice in separate scenes.
When Danny keeps suggesting show tunes as new songs, Keith says "What's next? Oklahoma! (1955)?". Coincidentally, Shirley Jones starred in that film and stage production.
The title is of a song written by Charles Chaplin for his movie A Countess from Hong Kong (1967), and performed by Petula Clark.
First mention of Bonnie Kleinschmidt (Elaine Giftos), Reuben's on-again off-again paramour. She will not appear until S02E15.