When examining the bookcase in Hawke's mansion, Hawke will mention that Varric recommended the book "The Pursuit of Knowledge" by Brother Genitivi. Brother Genitivi was a character in Dragon Age: Origins. He was a Chantry scholar who had spent his life studying the Sacred Urn which is said to hold Andraste's ashes. After meeting and saving Brother Genitivi in the Haven Chantry, the player could either decide to have him travel with you through the mountains outside the Village of Haven to find the ashes, which were needed to heal the Arl of Redcliffe, or to send him back to Denerim.
While in The Hanged Man with Varric Tethras he can be heard saying, "I like this bar, everyone here knows you name". This is a reference to the theme song of the popular American sitcom television series Cheers which ran from 1982 to 1993.
In Act 1, if you talk to the bartender at The Hanged Man then he may say something about the rapid decline in the pigeon population in Ferelden. This is a reference to Shale from Dragon Age: Origins.
If you speak to Varric in The Hanged Man, he will make a comment about a serving girl named 'Edwina'. This is a reference to Baldur's Gate 2, where the mage 'Edwin' is turned into a woman at the end of the game.
Contributed by Hipserious
Shale was originally meant to appear in Dragon Age 2, but this was dropped in favor of Natheniel from Dragon Age: Awakening.