What is an obscure piece of media or videogame that you think nobody else here has heard of?

I've never seen a video on this, but surely someone else has heard of it.

Back in the late 2000s, early 2010s, I got a CD in a cereal box with a PC game on it. the game was I think some kind of gamified flight sim, and the interesting part is that there was a decal of a plane on top of the CD surface. On the other side of the CD, there was another game (maybe a racing game?) And it had a corresponding decal, so the CD had decals on both sides and could be inserted both ways in your player to play each game. I've never seen that anywhere else (2 -sided CD or CD readable surface with decals) and I remember the game actually being somewhat fun, but promotional games of the era are very often lost media.