After entering the Denerim Market District at least 42 times, there is a chance that a random encounter dubbed "Zombie Kitten Army" can appear, spawning a group of 9 unmoving cats in formation.
At one point in the game, The Warden can obtain a long sword named "Oathkeeper". The sword is described as a blessed blade commissioned by The Chantry and given to Templars as a reward for their deeds. It has been speculated that the sword is a homage to George R.R. Martin's book series "A Song of Ice and Fire", as the sword shares the same name as the sword given to Jaime Lannister by his father Tywin, which Jaime later passes to Brienne of Tarth who then names the sword. It is known that the book series was an inspiration during game development.
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..."
Originally, the character Shale was meant to be the size of the other golems in the game. However, the developers had trouble with her fitting through doors and originally cut the character entirely. Thanks to a delay in the release schedule, they had some extra time and decided to create a new, smaller character model for Shale. This is referenced in the game as she said she was "chiseled down" by her previous owner.