I have a theory that Amber is going to be *added* to the season credits about halfway through the season. This will theoretically happen after she is gone for about 4 or so episodes, and where Willow gets darker and darker. More on this in a bit.
The reason Amber wasn't in the Season 5 credits is fairly obvious. Michelle Trachtenberg was joining the show, Marc Blucas was still there, and between Emma Caulfield and Amber Benson, Emma made the most sense. Emma had been with the show since Season 3, while Amber had just joined halfway through 4. The credits were now Sarah Michelle Gellar, Nicholas Brendon, Alyson Hannigan, Marc Blucas, Michelle Trachtenberg, James Marsters, and Anthony Stewart Head - pretty crowded. Adding Amber would have made it even more so.
With Season 6, however, it suddenly made less sense. Anthony Stewart Head was no longer in the credits, Marc Blucas had left halfway through season 5... So why wasn't Amber there? Tara was a very prominent character in the Season Premiere, and has continued to be so throughout the season. Most people on other boards just assumed it was because Tara was leaving, or would be killed off in the future.
My theory, however, is that Amber wasn't signed as a regular this season because Joss *wanted* for Tara to be gone for a while. Though he loves her, he knows that Tara being there would dramatically change the development of the upcoming Willow storyline (be it "Dark Willow" or "Willow becomes a magic addict") Everyone else is too wrapped up with their problems right now to truly understand what is going on - Buffy with Spike, Xander with Anya, Dawn with being a fifteen year old girl... If Tara was there, she would probably everyone fully aware of what was going on, in the same way she has apparently done with Giles. With Tara and Giles gone, however, (the most likely ones to stop her initial descent), Willow can truly hit rock bottom.
In spite of this, we know that Tara isn't gone for good. Amber Benson is scheduled to star in at least 16 episodes this season (if not more), and my theory is that after a brief hiatus, Tara is going to return and then be *added* to the credits.
But she's not a season regular, you say! Well, neither were Marc Blucas or James Marsters, and *they* were added part way through Season 4. If you watch the early episodes that season, you see the credits are Sarah Michelle Gellar, Nicholas Brendon, Alyson Hannigan, Seth Green, and Anthony Stewart Head. That's it. And while Seth Green's departure probably had something to do with one of them being added (as a new slot had opened up), I'm guessing that it was always planned that Marc Blucas would be placed in the credits. Joss had the whole Initiative storyline in his head, but didn't want for Riley to have to appear in *every* single episode from the beginning. He thus introduced him in episode one, had him appear sporadically over the next several episodes, and then finally added him to the credits halfway through, much the same then happening with James Marsters.
We now have something similar happening with Amber, but taking place in the middle rather than the beginning. It looks like Joss didn't want Tara to be there for a while in order to further the current Willow storyline, and so she wasn't signed as a regular. There are undoubtedly other reasons as well, such as this gave Amber more time to appear in movies and meant she didn't have to do as many convention appearances... but I've come to believe that this was one of the major reasons.
In any case, it seems very likely that Tara is going to be distinctly important in the second half of the season. The Willow storyline is shaping up to be a major one (even beyond Buffy/Spike), and since Tara is such an important part of Willow's life, she makes the most sense as a key character towards the eventual confrontation and resolution. My guess is that Tara is going to end up having more screen time than she's ever had with this series, and during that time will finally be added to the opening credits.
I understand now why Tara wasn't added there before, she's going to be missing for a while so things can reach an appropriate level of Buffy trauma. But Tara *is* going to return, and when she does there will be no such reason to keep her from it. Joss has stated repeatedly how much he loves Amber Benson and the character of Tara, and considering the credits are currently nowhere near as crowded as they have been in the past, that would be the perfect time.
That's my theory anyway. I really hope it's true, as it would give great hope to all the kittens out there, and grant Amber Benson the recognition she so richly deserves.
Addendum - Whoops, I forgot to add an apostrophe in the message title. Can anyone fix that?
[This message has been edited by Blixxt (edited November 13, 2001).]