Within Portal 2, both in-game and in the trailers, are multiple references. There are a variety of references, mostly including games or parts of games.
General References
- The achievement, Schrodinger's Catch, is a reference to Schrodinger's Cat, in which a cat is exposed to a neurotoxin that has a 50% chance of killing the cat. His theory dictates that the cat is both alive and dead while the box is sealed. The experiment is also referenced by GLaDOS in the Lab Rat comic when she requests boxes, cats and neurotoxin.
Games
Left 4 Dead series
- During one of the pre-release trailers, Atlas can be seen wielding the frying pan, a weapon used by the survivors in L4D2.
Smash TV
- One of the achievements labeled Smash TV is a reference to an early 90's arcade game called Smash TV, where two contestants are pitted in a brutal game show in which they're forced to fight for their lives for cash prizes.
Movies
- The achievement, Stranger Than Friction, is a reference to Stranger Than Fiction, in which a man finds out his life is being narrated like a novel.
Music
Song
- The achievement Bridge Over Troubling Water is a reference to Simon & Garfunkel's song Bridge Over Troubled Water.
Other Games
- The achievement Narbacular Drop is a reference to a puzzle game of the same name, Narbacular Drop. It was the Portal team's first game, from which Portal was based off of.