I watched The Big Bus last night, which is kind of an Airplane-type goofy comedy that predates Airplane by four years. As with that later film, the jokes sometime go hard and fast, and when you have that density of jokes, you can afford to put in ones that only a few people (like, say, librarians) would get.
At some point during the film, the driver discovers a bomb underneath the bus. When he tells his girlfriend about it over the walkie talkie, she asks him if it has a red and white dial in the bottom right corner. When the driver says yes, the camera cuts to her in the front of the bus reading from an over sized blue book titled Jane's Book Of Bombs.