John Keating co-stars as recurring character Ernie Moran. He was credited as Celt #4 when he appeared in Season 1 and the character was not named until he recurred in Season 2.
| 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 |
| Season two appearances | |||
| 21 | Ourselves Alone | A Dangerous Maid | What Does the Bee Do? |
| Gimcrack & Bunkum | The Age of Reason | Peg of Old | Two Boats and a Lifeguard |
| Battle of the Century | Georgia Peaches | Under God's Power She Flourishes | To the Lost |