The Tetris license has had more than its fair share of issues, with various companies claiming rights over lots of different platforms. In the middle of this struggle Sega decided to release a version on the Megadrive, despite only having a very flimsy claim on an already chaotic console release agreement.
Right as it was about to release, Nintendo managed to press their claim and Sega were forced to recall and destroy most of the copies. A few hundred got out into the wild, making this truly one of the Rarest games on the Megadrive.
Sega repurposed it’s popular Megadrive platform to use in the edutainment market. In doing so they added some truly interesting ideas to make the Pico.