The reason Desi Arnaz thanks the The United States Steel Hour (1953) at the conclusion, is when this episode was finished being edited, it's runtime was 75 minutes (that's including adverts. Without any commercials, it's 55 minutes). They were told to trim another 15 minutes, but desi said it was impossible. The The United States Steel Hour (1953) graciously offered to release the extra time for this episode.
Lucy's good friend, Susie McNamara (Ann Sothern) is Ms Southern's character's name from the series, Private Secretary (1953). This was one of the earliest (if not first), so-called 'crossovers', wherein a character from one series appears on another.
Desi Arnaz created The Lucy-Desi Comedy Hour (1957) as a continuation of I Love Lucy (1951), and was originally announced 2 years earlier (it was to be shot in colour). It was envisioned to run every 3 weeks, but, due to the series' extremely high production costs (originally estimated by Desilu at $250 thousand for each episode) and other factors (getting sponsors - both sponsors off I Love Lucy (1951) - General Foods and Proctor & Gamble, pulled out due to high cost and limited runs. Ford finally agreed; as a way to promote their brand new car; the Edsel) , it became a limited run series.
Barrie Chase appeared briefly as a background dancer in the "Our Ship Is Coming In" number with Desi Arnaz and Cesar Romero. When the show reran (July,1962), CBS promoted Barrie as a guest star. By that time, she had become well-known as Fred Astaires dancing partner on 3 acclaimed TV specials.
Both Cesar Romero, with the character role of "The Joker" and Rudy Vallee with character role of "Lord Marmadue Ffogg" appeared as two of Batman's villains and rivals often on Batman (1966).