There is a reference to the game "Portal" toward the end of Dragon Age: Origins. To find it, you must have Sten in your party. At the end of the game, if you choose to perform the ritual with Morrigan, you will go to the crowning of the new king or queen. After the dialogue with Alistair you can walk around and speak with your companions. Find Sten and he will say "Where is the cake? They promised there would be cake. The cake is a lie..."