Casting Gag: Alistair deeply distrusts magic and was a former Templar. In real life, Steve Valentine is an accomplished stage magician.
Executive Meddling: This and time restraints are the reason Shale's only available via DLC instead of being in the vanilla game.
Though the devs were kind enough to include that bit of DLC for free with any copy purchased new. It still served to discourage buying the game used (which doesn't turn a profit for BioWare). It was later made free in Summer 2013 as part of EA's removal of Online Passes.
Meme Acknowledgment: Dragon Age Keep allows you to create a story to import into Dragon Age: Inquisition without having to play the other games. In the Companions section for Origins, it refers to the ritual child that Morrigan can conceive with a male Grey Warden as an "old god baby."
Playing Against Type: While playing a villain is quite standard for Tim Curry, it is incredibly rare for him to be one of the most subtle and repulsive villains in the entire story.
Serendipity Writes the Plot: None of the Qunari had horns although their race is supposed to have them. This was because BioWare didn't have the time to create alternate designs for all the helmets just so your Qunari party member could wear them, so they opted to not give him horns at all and Hand Wave it by saying that Qunari born without horns are considered to be destined for greatness, while those who choose to leave the Qun cut off their horns as a way of showing their rejection (all the other Qunari in the game).
Shrug of God: When asked about Maric's cause of death, David Gaider repeatedly stated that it was irrelevant before finally revealing that he was lost at sea. The Silent Grove reveals that he was rescued from drowning, was imprisoned by the Antivans only to be captured by a Tevinter Magister. Unfortunately, when Alistair rescues him in Until We Sleep, he is forced to give his father a Mercy Kill.
Urban Legend of Zelda: There was a rumor (and rumor only) that if you do not kill Flemeth in Morrigan's sidequest, the ending epilogue will state that Morrigan was killed and possessed by Flemeth. Said rumor only ended when it was Jossed by the series' head writer.
Jowan was originally planned to be a companion and recruited via the Right of Conscription after the Redcliffe arc, who would teach the Blood Magic specialisation, but the developers couldn't fit him into the rest of the team due to there already being a huge number of characters (none of whom knew how to conduct the Joining anyway).
The Avvar Barbarian and Human Commoner from Redcliffe origins were considered, the former even having some concept art designed, but sadly never got off the drawing board and were cut early in development.