Doom mini marine

Doom mini marine is the cutest secret ever

Id Software channel a variety of sources for Doom secrets, including Skyrim and Terminator 2, but their best is the Big Hero 6-esque Doom mini marine. So cute.
Okami

The Death of the Demo

Back when gaming magazines ruled the games journalism space you would often receive a free gift with your purchase of a videogames publication. That free gift, more often than not, would be a demo disc.