I’ve never read a James Stewart biography (are there any good ones?) but I’ve read a lot about him and I delivered some files (i.e., quotes and stories based on phone interviews) to People after he died in July 1997. And I think it’s safe to say that in the 1930s he was quite the ladies’ man. I’m mentioning this because I suspect that a reason why he enjoyed telling this joke was because of his randy past. I’ve never read that Stewart was anything but 100% loyal to Gloria, his wife of 45 years, but you have to know a little something about catting around and the pure animal joy of erections in order to tell a joke about catting around.