There are hidden messages in the splash of the game launcher. You can see what they are by using the Print Scrn key on your keyboard to copy the screen to memory and then paste it in a picture editor (MS Paint works). Then use the Fill-With-Color tool and fill the black parts between diablo's horns with white, strings of text written in slightly different shades of black would stay black, and be revealed. The area between first and 2nd horns says "Buy War2", referring to Warcraft 2, and the area between 2nd and 3rd horns says "Natalie Portman Rocks.
A sound file of the game's namesake, apparently speaking in tongues, is played when entering level 16. It can be extracted from the game's main data file and, when played backwards, produces "Eat your vegetables and brush after every meal." This is a play on the claim that satanic subliminal messages perceived to be included in songs through backmasking effectively lead teenagers towards sex, drugs and violence.
When the Diablo game launcher is opened, the game plays a deep, evil laugh (often assumed to be that of Diablo). When this laugh is recorded and sped up several times, it becomes the sound that Scavengers emit upon death.
I've been playing Diablo1 with my girlfriend every now and then and found these facts when searching about Diablo1.
