It's been almost 20 years since Pokémon Diamond & Pearl were released in Japan. That's two decades of taking Piplup, Chimchar, and Turtwig on adventures through Sinnoh, meeting the other 148 Pokémon in the Sinnoh Pokédex along the way. It's probably safe to say that you know the designs of the DS 'mon pretty well by now after all that time, so it's a surprise to see a whole bunch of never-before-seen designs made by Game Freak being revealed in a documentary.

The source of this new release is a collector called @neos_tcg who has picked up the DVD of the private Game Freak documentary, presumably made to show off the new Pokémon internally to other members of the company, a little like the style guides that were made to explain the notion of Pokémon to gamers in the West when it first launched in the US.
The documentary has now been uploaded to YouTube, and Pokeos is in the process of uploading the full beta Pokédex for fans to check out how their favourite critters could have looked. It's interesting to see the different design processes in the video, and thanks to auto-translate on YouTube, I can read the subtitles to see what the designers were thinking when they initially put pencil to paper.

Looking at how Dialga's design could have turned out is really fascinating. It's the same for all of the Pokémon shown, especially the likes of Turtwig, who looks more like an armadillo in these early sketches. Infernape looks a little like something you'd find on a Mayan statue too!
Check out the video, and have a good scroll through Pokeos' new Beta Pokédex. And then when you're done, take a look at the Timeless Diamond and Spaceless Pearl ROM hacks - Pokémon Diamond and Pearl evolved!