After a scheduling mix-up with Adam Baldwin for “Bad Angels,” Mercedes McNab struggled at first to get questions and even pleaded with the audience to fill the silence of two Centennial ballrooms.

Then, questions started flowing from the microphone-shy fans. McNab seemed to recover from the awkwardness and even enjoyed the questions about her career and her time as Harmony on Buffy the Vampire Slayer and Angel.

One question, “Was she aware that she was the longest-running character in the Buffy universe?” had her purring, “I am.”

But McNab sighed in relief as Atlanta resident Ken Feinberg, the Chaos Demon with the antlers from Buffy, surprised her by taking the stage.

“Thank God! I was dying up here by myself,” McNab said.

Feinberg swooped in to discuss his appearances on episodes of Buffy. “Acting on the series was a lot of fun,” he said.

His big disappointment: “They called me for Firefly, but I was booked on Alias that day,” said Feinberg, who also appeared in Charmed, The District, and Star Trek: Enterprise’s episode called “Horizon.” Feinberg will next appear in the romantic comedy, “Coming Clean, which he developed, cowrote and directed.

McNab treasured her time as Harmony.

“We always had fun,” said McNab, who auditioned for Buffy. “It never became a job. You just came to work and played.”

One day, the play turned too emotional in her dysfunctional relationship with a fellow vampire. Spike, played by James Marsters, threw her against a wall in disgust.

“I just started crying. It felt very real and the situation hit me. That’s the beautiful thing about acting. You live in that moment,” McNab said.

McNab will next appear in a romantic comedy called Dinner Party and was just offered a movie this weekend