One of the creators of Portal said that they didn't intend for The Cake is a Lie to become a meme. He also said that they intended for a random metal hoop that had 2 seconds of screentime at the end of the game to become a meme. According to him, they dubbed it "Hoopy the Hoop," and they had t-shirts, mugs, and all sorts of merchandice (supposedly) created for this hoop. However, I am pretty sure that he was being sarcastic when he said this, because "The Cake is a Lie" was such an integral part of Portal 1, whereas the random hoop at the end of the game was insignifcant. I do not see how they possibly could have thought that "Hoopy the Hoop" would be remembered, let alone acheive meme-hood, and I don't beleive that they actually thought that "The Cake is a Lie" would fail to become a meme.
Though certainly I agree that the little things become memes. "But then I took and arrow to the knee" wasn't intended to become a meme, and "All your base are belong to us" certainly wasn't. :P