Some topical jokes do age of course.
There is a goon show (from the 1950s) where they are out walking on top of a cliff at night in the fog.
They hear a persons voice, and one of them says "who would be out here on a night like this".
And someone replies "Lady Docker" at which there is a HUGE laugh from the audience.
I assume Lady Docker was some upper class lady at the time who would never have set foot on top of a cliff at night.
http://en.wikipedia.o...ki/Norah,_Lady_Docker