Chex Quest is a first person shooter / advergame developed by Digital Cafe and released in 1996. It used the id Tech 1 engine. It was bundled for free with boxes of the Chex cereal.
Chex Quest 2 released the same year. This was an addon and required the original game to play.
An unofficial sequel, Chex Quest 3 or simply "Chex 3" was released in 1996. It is notorious for having various content lifted from other Doom wads without permission.
A totally different Chex Quest 3 was developed by the original game's lead artist and released in 2008. It includes all the levels of the original game and the expansion, plus a new set of levels.
Chex Quest HD was released in 2020, and can be obtained for free on Steam. It includes the same levels as the original game, but remade with modern visuals on the latest Unreal Engine.