The Stanley Parable

The Stanley Parable is a game about choice, a British narrator, and the lack of (or, alternatively, the inclusion of) free will in video games. It's...hard to explain, to say the least.

Hidden Developer's Text
In an extremely interesting programming feat, the coders left a peculiar little file in thestanelyparable/bin – README.txt, which contains the word "sup". In the demo, this contains "hi timmy!" instead.

Old-School Cheats
There are a couple of secret commands that can be entered during gameplay, instead of in a console, that enable Easter eggs:
 * Typing facepunch during gameplay will replace most of the game's textures with a hand-drawn sketch of the Facepunch Studios logo. This is a shoutout to the Facepunch forums, where a lot of the development team originated.
 * Typing secret on the title screen, then clicking the "Credits" button will play a very silly kazoo song over the credits.

Console Easter Eggs
Certain commands entered into the developer console will result in Easter eggs instead of actual development things:
 * imabird: Enables the "flight" effect from the downstairs path/crazy ending during normal play.
 * hideous: Opens a Steam Overlay web browser window pointing to the Official Team Fortress 2 Wiki, opened to a random hat that Hideous (one of the 3D artists who worked on The Stanley Parable) contributed to.
 * raphael: Start a new game after entering this, and every line of narration will be replaced with "Stanley." in reference to a gleefully caustic teaser trailer wherein the Narrator responded to an email from a chap named Raphael.
 * sv_cheats 1: When entered into the demo, this works fine, but in the full version it will instead whisk you away to a secret map to get a stern talking-to from the Narrator. Repeat two more times for additional dialogue. See the talk page for a way to evade this behavior so you can noclip about merrily.

Stanley Parable Mod leftover
Inside the Narrator's sound directory is a file called boss1957.wav, a leftover for the original Half-Life 2 mod in which Stanley had to input 1957 (extra-extra secret PIN number in final game is 1947) on the keypad. The final game's keypad code is 2845, and has the new narration split between Boss_success_00.wav and Boss_success_01.wav. (In v1.4 for the original mod, this was done alongside converting the lines to MP3s to reduce size and support for Closed Captions.)