A very good way to show that your invention was not obvious is to find relevant scientific literature that "teaches away" from the way you solved a particular problem. So, for instance, if you find a textbook that says "you can never make a battery with these chemicals," but you make a perfectly functional battery with those very chemicals, you can get a patent for your battery. But, on the other hand, if other people have used something to solve a problem, and you're just changing out some basic materials or components or techniques, your solution -- even if it's an improvement over the state of the art -- is likely not worthy of a patent. Science ever advances, you see, but not all of it is patentable.
Sex toys, including dildos, can be patented (NSFW, NSFW, and NSFW, just to name a few). And you can buy a dildo made out of glass (NSFW). And we all know that, if your improvement to a device is innovative enough, you can patent your new invention. So the question presented in Ritchie v. Vast Resources, Inc. was, can a new glass dildo be patented as new 'n' improved, if we make it out of Pyrex?
Judge Richard Posner, sitting specially on the Federal Circuit, says no: making a dildo out of Pyrex rather than glass is too "obvious" to make the new dildo patentable (PDF, NSFW, especially if your workplace would ban the word lubricious). It's not enough of an innovative change; it was merely a novelty and a predictable variation in the, uh, market sector of glass sex toys.
It looks as though the patent holder argued that Pyrex isn't just smoother ("more lubricious") than ordinary glass, but it's also better than ordinary glass because it's resistant to electricity . . . presumably a desired quality for dildos in some people's bedrooms. I, uh, wouldn't know about that.
In closing, I'll paraphrase KSR v. Teleflex, 550 U.S. 398 (2007):
The proper question to have asked was whether a [dildo] designer of ordinary skill, facing the wide range of needs created by developments in the field of endeavor, would have seen a benefit to upgrading [glass dildos] with [Pyrex].(I don't have the U.S. Reports pincite for that paragraph handy, but it's near the end.) It's difficult to get a patent declared invalid; there's a heavy presumption in favor of the Patent Office's decision to award one in the first place. Judge Posner did it in 6 pages.