Chex Quest is a non-violent sci-fi first-person shooter developed by Digital Café (with the cutscenes being created by Shank Studios) and released in specially-marked Chex breakfast cereal boxes in 1996. It is known as the first computer game distributed as a prize in cereal boxes (and is also known as the most popular of its kind, developing a cult following). It uses the id Tech 1 engine and is a commercial total conversion of The Ultimate Doom (as indicated by the leftover accessible content).
Players control the Chex Warrior, an officer from the Intergalactic Federation of Cereals (who wears an armor identical to a piece of Chex cereal) who is sent to the planet Bazoik to fight off an invasion by slimy, green creatures known as "Flemoids". Because conventional weapons are ineffective against them, the Chex Warrior must use an array of devices called "Zorchers", which teleport them back to their own planet. However, the Flemoids are not eager to cooperate, and will attempt to cover the Chex Warrior in slime (if the Health meter reaches zero, the Chex Warrior is too "slimed" and unable to move, resulting in a game over).
The game received two official sequels: Chex Quest 2 (in 1997 via the Chex Quest homepage, now defunct) and Chex Quest 3 (in 2008 via Digital Café lead artist Charles Jacobi's personal site). Despite not being official Chex products (and not released in Chex cereal boxes), both were created by members of Digital Café. In addition, Chex Quest 3 includes the original Chex Quest as an "episode", updating it to an improved source port of the id Tech 1 engine.