It took me a long time to figure out that they were intended to make you feel good about yourself somehow. I was, for some bizarre reason which now makes no sense whatsoever to me, under the impression that they were called 'Happy Jacks' as well. That's not exactly a morose handle. Maybe because I've been starting to feel that the Who were actually a bit shit album-wise recently or something. I don't know.
edit: oh, and they supposedly have some amphetamine like qualities and yet they would seem to have destroyed my appetite entirely. Strange.