Ricky claims to have gotten tickets for the opening night of a new Rodgers and Hammerstein show. Although "South Pacific" and "The King and I" were still playing on Broadway at the time the show was filmed and aired, there was no new Rodgers and Hammerstein show until "Me and Juliet" in May 1953.
When Ricky enters the bedroom near the end to see Lucy and Ethyl's handiwork, Fred can be seen in the doorway waiting for his cue. He steps back out of frame after Ricky and Lucy enter.