A good hint would be that you can use a standard text editor to read the games language files. I just "found" my easter egg this way while still glowing green from solving the radiation level...

Well that's a bit of cheating ;) With this at least one of them gets obvious.
So if you don't want to do this I can give you a hint that all of these so called 'eastereggs' can be found in console.

Yeah I figured it had to do with the console, but I didn't screw around there very much :B

console?
so you have an achievement that's not even part of the game? that kinda sucks..
usually dont like to having to look up walkthroughs on how to get achievments, but seeming as I know nothing about the console (or how to even open it) that doesnt leave much choice.

Oh, you've misunderstood me. I meant the 'console' in game - terminal that is available before every level under the story text (where you click the 'Continue' button). You can type there commands.

Ahh I see, hadnt even noticed that particular screen was interactive before.
After much messing around, I just ended up just reading the language files like the first guy said.. and even after reading the stuff in there, I still dont understand how to unlock the achievement.. it certainly isnt 'obvious' like you say.

There is a certain game company associated with one of the most popular cheat codes of all time. Try entering that code. The name of the company is mentioned in the easter egg section of the language file.

Yes, that's what I meant by obvious :) All other eastereggs involve using one of the commands that are displayed after you enter 'help' command in the terminal.

The console accepts the [REDACTED]

I know the cheat code you're referring to, I just cant find a way of entering it that doesnt result in the unknown command error.. and I'm so very sick of that error.
Anyways if I keep trying to get this easter egg achievment I'm going to end up punching a hole in my screen, so might be best if I just give up on it I think.

edit: nevermind, I see that I just pointed out the cause of my mistake right there.

iddqd and idkfa don't work :P

Hey guys !
Have the same issue here. The easteregg achievement is the last one I don't have and I can't find how to get it.
I tried the langage file like Yves suggested and found the easteregg part in it.
But don't know what to do now.

I tried every command followed by any clue I get from the langage file like wheatley, aperture, konamicode, etc but got an error syntax.

How did you do, Saintanik ?

Eieiei. Thats a horrible one. I tried a lot of combinations of the given commands with the help function. Nothing is working. And I don't know where the language-file is hidden at my linux system. There is no folder which is called prelogate.

This is poking in a dark box. I've no clue at all. It has nothing to do with logic like the rest of the game, which is quite cool.

A frustated Weihnachsthase

I don't know if you need to be in the terminal screen for this, but just try entering the Konami-Code.

Weihnachshase > You can get the achievement by entering the Konami Code (arrow up, arrow up, arrow down, arrow down, left, right, left, right, B, A, Start) in the terminal