As of right now there are approximately 720 Pokémon - roughly five times the original count of 151. Their designs have encompassed the good, the bad, and the terrifying. But as Zygarde's new form reminds us, continually coming up with new ideas for Pokémon is really hard.
In case you missed it, Zygarde's new forms were revealed a couple days ago. They run the gamut from cell-like to dog-like to... Well, judge for yourself.
Barring the weird mix of colors, it's not actually that dissimilar from your typical Pokémon design tropes. The monsters have been trending toward the sleek, almost plastic look seen in Zygarde's new form since at least Pokémon Black and White. The long arm shields/wings bring to mind, weirdly enough, Lopunny from Diamond and Pearl. In many respects, it fits right in.
In many other respects, though, it doesn't work. I'm not going to sit here and try to break down its design for you, because franky, I'm not an artist. But to my untrained eye, it looks messy, not the least because of its rather random red, green, and blue color palette. It's an appreciable step back from the original Zygarde, which meshed the look of a snake and a slug into a distinctive looking monster. With the new form, I have no idea what I'm looking at.
But after some 720 monsters, it's not surprising to see Game Freak reaching a bit. They more or less exhausted all of the common animals and mythical creature archetypes in the first 250 or so designs. They've regularly gone back to birds, dogs, and cats over the years, but their other designs have gotten quite a bit more esoteric, sometimes for the better, sometimes for the worse. The intial shift was evident in Ruby and Sapphire, which introduced monsters like Latios and Latias - dragons who look vaguely like jet planes. And it's gone on from there.
What's impressive, I suppose, is that Game Freak has managed to keep the design quality comparatively high over the years. Among their stable designers, Game Freak has benefited from the talents of Ken Sugimori and Atsuko Nishida from the very beginner - designers of many of the most memorable monsters. It was Nishida who created Pikachu, the plump yellow rat who would become as ubiquitous Mickey Mouse. Both of them are still at it, with Nishida being responsible for Sylveon, and Sugimori developing Xerneas and Yveltal.
It's their talents, and a host of others, that have propelled Pokémon over the years. Good as the games have been over the years, their memorable (and very marketable) designs have helped to put it over the top and make it the global machine that it remains today. The new Zygarde form is just a reminder of the degree of difficulty in coming up with yet more unique designs.
It's honestly hard to say where the series will go from here. It will continue, of course. Sales remain brisk, the anime is still (!) going after more than 15 years, and Game Freak keeps cranking out new monsters. But this is also the first year since 2008 that we won't be getting a new game to play. Game Freak, it seems, is considering its options with this series. Pokémon Go is evidence enough of that. And with the explosion of Yokai Watch in Japan, they are wise to do so, as they now have some real competition.
For almost 20 years now, though, they've managed admirably to keep cranking out memorable monsters. And though the new Zygarde form is definitely a clunker, there will undoubtedly be many more to come.