A few months ago, I purchased a copy of The Annotated Marx Brothers: A Filmgoer's Guide to In-Jokes, Obscure References and Sly Details by Matthew Coniam. It's an in-depth look at the brothers' films telling you every little detail you could possibly want to know about the making of the movies and, more significantly, all the cultural references and little mentions that are now historically obscure. Like in A Night at the Opera, there's an exchange that goes…
GROUCHO: Don't you know what duplicates are?
CHICO: Sure! Those five kids up in Canada!
If things like that mystify you — if you didn't know it was a reference to the Dionne Quintuplets born in Ontario in 1934 — then you need this book. It puts a lot of what's in those films into proper historical context and clues you in as to what some of the obscure lines mean.
It's one of those "must-get" items for anyone interested in Groucho, Harpo, Chico and even — and yes, some people are interested in him — Zeppo. When I can read a book about the Marx Brothers and learn stuff, that's got to be a great book.
I meant to tell you this and to post a link to order when I first got it and started reading but I somehow never got around to that. Thanks to Marx Fan extraordinaire Bob Gassel (who assisted with some research, I believe) for reminding me I wanted to remind you that you want this.