As TV Guide Online previously reported, after two years of semi-regular appearances as demon Anya on Buffy, the Vampire Slayer, Emma Caulfield finally becomes a full-fledged regular this season. Now, series creator Joss Whedon reveals why he waited so long to promote the Beverly Hills, 90210 alum.

"Making someone a regular is not something that we take lightly," Whedon tells TV Guide Online. "Somebody can do really well, but it's a question of, 'How do they fit into the group dynamic? What need do they fill?' It's a delicate thing."

In the case of Caulfield — who relents, "everything happens at its own pace" — Whedon eventually saw that she was just the person to fill the wiseacre void left when Charisma Carpenter's Cordelia jumped to Angel. "She speaks her mind rather bluntly and feels a little bit on the outs with people, so it makes perfect sense," he says. "And Emma's extremely funny. You don't usually get that much funny in a girl that pretty."

Well, things may get pretty ugly when Buffy's little sis Dawn (Michelle Trachtenberg) develops a crush on Anya's main man, Xander (Nicholas Brendon). And although Whedon is coy when asked if the 1,120 year-old patron saint of scorned women will get her powers back — "There's always a chance: This is Buffy! — he does hint that issues from her dark past may resurface. "Her relationship with Xander is something that we really want to explore, and we also think she has such a fascinating history."

One development Buffy fans won't be treated to, however, is any type of hanky panky between Anya and fellow demon Spike (James Marsters). Despite some winning chemistry displayed between Caulfield and Marsters late last season, Whedon says it probably won't become love at first bite. "Emma and James are both very funny and it was great to see that dynamic because we never have before," he says. "But it's not like we're planning a romance or anything. But we definitely thought, 'Well, that works.'"