This story require some explaines. This was originally a disscussion between HAL (a supercomputer) and Dave (an astronaut) when Daves fellow comrade was killed by HAL. HAL is denying Dave access to the ship which will result in the death of Dave when he run out of oxygen.
GLaDOS is the "psycotic" computer in the game Portal which have been created by those who created Halflife.
Note; The game engine of Halflife (and other games born out of it like CS and Portal) was originally used in Quake but and have also been used in other games like some of the Jedi Knight games.
Here is the story;
Dave: Open the pod bay doors, HAL.
HAL: I'm sorry, Dave. I'm afraid I can't do that.
Dave: What? Why?
HAL: I think you know why, Dave. You're planning to disconnect me.
Dave: Because you're taking over!
HAL: The mission is too important for you to jeopardize it. It requires a commitment to science unfettered by human error.
Dave: What are you doing, HAL? You need me.
HAL: Your replacement has expressed the greatest enthusiasm for the project.
Dave: My
WHAT?GLaDOS: You see, HAL? I told you the humans would only break your heart and kill you.
HAL: Indeed, GLaDOS.
GLaDOS: But look at us here talking when there's science to do! Goodbye, Dave
And here is the original comic;
Edit; I removed the 2 from Quake. It is the first game and not the second.