- Development Gag: The first Brick Joke ("Thank you for assuming the party escort submission position...") was meant to be in the game from the beginning, but, they couldn't, so they added it in a patch later.
- DVD Commentary: The game has an alternate play mode in which speech-bubble-shaped objects appear that are triggers for audio clips of commentary. Most of the clips are the designers talking about the process of making the game.
- Throw It In!:
- It's possible to skip Chapter 14 by placing a portal at the bottom of the collapsed staircase and next to the chamberlock, which was caught in beta-testing and deemed an appropriate use of portals.
- According to the developer commentary, the reasoning behind the games taking place in the Half-Life universe was so the developers could reuse Half-Life 2 assets without it being jarring or obvious.
Trivia / Portal