Despite the focus on the core cast, there were plenty of new characters. My favorite was the female football coach, Beast (Dot Jones, The Boondock Saints, Patch Adams). She was introduced as a stereotype, but was fleshed out and sympathetic by the midway point of the episode. As much as I loved the Will (Matthew Morrison) and Sue (Jane Lynch) team-up, I loved even more when Will followed his moral code and apologized to Beast.
Other new singers were also introduced. Sam (Chord Overstreet) is a new kid who gets Finn's place on the football team, and rejects the club to be cool. Sunshine (Charice) was a threat to Rachel's place in New Directions, until the diva alienated her enough to send her into the arms of their arch-rival, Vocal Adrenaline. Both could be really cool characters, and I look forward to their return.
Part of what makes Glee succeed are the cast of recurring minor parts, and the premiere did not leave them out. "Audition" opened with great documentary interviews provided by Jacob Ben Israel (Josh Sussman, Warren the Ape), and Becky Jackson (Lauren Potter) sat in on Cheerio tryouts with Sue. I would be remiss if I did not mention Principal Figgins (Iqbal Theba), who had more than the usual refereeing to do in the first episode back.
All in all, it was an unexpectedly awesome start for Glee's sophomore season. If they can maintain the fine tuning to an already hit formula, this show will only go up from here. Kudos to all involved.