There’s no denying that Pokemon is one of the most kid-friendly franchises out there (child abductions and dead spirits that come back as pokemon notwithstanding,) and that it’s on the opposite end of the spectrum as the mature manga/anime Attack on Titan. Nobody thinks that the two franchises will ever mix, especially in game form.
At least, nobody outside of the indie dev team Arcane Kids, who just released a video showing off a new game based off PokemonNXT, titled Pokemon Millennial Edition. If you’ve been paying attention to the first paragraph, Millennial Edition is a game that mixes elements from Attack on Titan and Pokemon. Basically, it puts players in the shoes of a Trainer, who is armed with a gun that shoots pokeballs and a crude version of the 3D Maneuver Gear. The target? GIANT POKEMON roaming the island.
As you can see from the video, the game is playable but nowhere near any form that would be considered fit for release. Arcane Kids will not release the game, with the video serving merely as a proof of concept for now. But there are other games at their retro-inspired (I think) site at arcanekids.com