Duncan O'Connor, played by co-star John Treacy Egan, is a supporting character in "Nights in Ballygran". He attends the Order of Ancient Celts annual St. Patrick's Day dinner and sings "Carickfergus". The dinner is later broken up by Prohibition Agents.
|Season one appearances|
|Boardwalk Empire||The Ivory Tower||Broadway Limited||Anastasia|
|Nights in Ballygran||Family Limitation||Home||Hold Me in Paradise|
|Belle Femme||The Emerald City||Paris Green||A Return to Normalcy|