"Did you discover the prototype Hunter?"
The Hunter, Episode Two's relentless new enemy, was already in Valve's collective minds by the time Episode One was being developed. And here's the proof - a prototype of the mini Strider. You can't see it on 360 or PS3, as there's no 'console', but on PC just type in the following commands:
"I see the Valve designers really like Lost"
Episode Two's action is interspersed with two references to hit TV show Lost. First, there's a blocked off room early in the game's mine location, which holds a computer that should be familiar to any Lost fans, complete with blinking line of numbers. Second, eagle eyed gamers have spotted a clear use of the Dharma Initiative's logo printed on a wall.
"Did you see all the info on the Aperture Science website?"
Part way through Portal you discover a grimy room outside of your lab environment, with writing scrawled all over. One missive reads "cjohnson" and "tier3". Use this info to login to the ApertureScience.com webpage, and type 'notes' to read a history of Aperture Science's technologies and research.
Or, use the login 'Admin' and the password 'Portal', then type 'Thecakeisalie' for an amusing/chilling message from an Aperture Science staffer. You can check our Portal guide for more commands.
"The cake isn't a lie - and I have the recipe"
Later in the game you'll come close to the same monitors that can be spotted through the warped glass of the test environments. And, spooling endlessly across them, is the garbled recipe for the mythical Portal cake. Yum.
"Aperture Science are keen on beating Black Mesa"
During Portal's endgame, you'll have two chances to catch Aperture Science's take on Black Mesa and how it plans to compete in the lucrative Department of Defense contract market.