Vincent Kartheiser spoke to the BBC about being cast as Connor:

“When I first got the sides [casting description] for the audition, it was for a role called Street Kid. They did not want to let out anything about the character, but what my agents would tell me is that, “this isn’t the character you’re playing, it is just an auditioning piece and the actual character will be very different from this.”

So I went in and I auditioned for it. It was a very basic scene, and I auditioned for Tim [Minear] and, I believe, Joss and David Greenwalt. They said, “Well, we really liked you a lot, and we’d like you to meet the cast next week.”

I went and met the cast, [who] all seemed very friendly, and then they brought me in for a screen test. They bring in all the cameras and the lights and the set and everything to see how you fit. It’s mainly for the studio, for them to give it the once over.

So I did that with David, and then, right before they told me I made it, they called me up and said, “We want you to know what kind of character this is.” They let me know that I was going to be playing Angel’s son, a demon killer from Quor’toth. I was excited because I’d never even imagined to play anything like that before.”