There are comments in all movies that don't need explanation to their original audience, but many times leave me mystified. This one mentions going to the movies for "bank night". I have run across this one before but didn't remember exactly what it was. It was a lottery with the winners announced at particular movie showings. A movie ticket wasn't required to claim your prize, so it didn't run afoul of gambling laws, but most people paid to watch the movie because you had to claim your prize within a short time. I have heard the term "bank night" in movies several times without it ever being given any real context.
The rich family also mentions being one of "America's 60 Families". This was the title of a 1937 expose by Ferdinand Lundberg who used tax records to discover that America wealth and power was controlled by only sixty families, which he listed.
Lastly, upon seeing an ill-favored cousin and his wife, Katharine Hepburn says "For the love of Pete... it's the witch and Dopey!". Snow White had just come out in 1937.
Grant and Hepburn were terrific. Also Edward Everett Horton.