When Errol Flynn dons a disguise as Humphrey Bogart, it's Bogart himself who's doing the voice-over.
At the beginning, Ellen tells the clerk her address is 840 Fifth Avenue. This was once the famous address of the "new" Astor mansion. It was the largest private house on Fifth Avenue from 1893 to 1927 when it was torn down. A Jewish temple now occupies the site on Fifth Avenue at East 65th Street, across from Central Park. Phil gives his address as 156 Central Park West, which is also the site of a church at West 76th Street.
Near the beginning, the daughter of Philip Gayley (Errol Flynn), Philippa Gayley, reads the note he composed for her, which he signed "Robin Hood". This was one of Flynn's most famous roles (Les aventures de Robin des Bois (1938)), though he wasn't nominated for an Oscar for it.
(at around 45 mins) Philip Gayley (Errol Flynn) says something about the possibility of spending Christmas in Connecticut. That is an inside joke because S.Z. Sakall (Luigi) was one of the stars of Joyeux Noël dans le Connecticut (1945).
(at around 45 mins) After thinking she'd seen him just a few minutes ago (though it really was Phil in a Santa Claus suit), Ellen tells Rex (in his Santa suit) to go downstairs and "for heaven's sake, don't drink any more Tom and Jerrys". When Rex gets downstairs, he asks Mrs. Hamilton if he has time for a little drink and how he looks. Mrs. Hamilton starts to say she already told him how he looks (It actually was Phil.), but aborts the statement and simply says, "These Tom and Jerrys must be stronger than I thought." A Tom and Jerry was a traditional holiday yule-time drink that originated in England in the early 1800s and was quite popular in the U.S. up through the 1950s. It is made with cognac, dark rum, whole milk, and a Tom and Jerry batter that is made with eggs, sugar, cream of tartar, and more dark rum. It is garnished with nutmeg, cloves, and allspice.