Ex-'Angel' star guesting in season finale

LOS ANGELES -- Former "Angel" star and current "Alias" bad girl Amy Acker will get to lighten up a bit come May, when she appears on CBS' "How I Met Your Mother."

Acker is scheduled to guest-star in the comedy's first-season finale as a woman who had a fling with Barney (Neil Patrick Harris). Her character also has a knowledge of Native American rituals, which comes into play in the episode -- and that's all we feel we can say at the moment.

Her guest appearance will reunite her with another former denizen of the Buffyverse, "Mother" star Alyson Hannigan. Alexis Denisof, another "Angel" regular (and Hannigan's husband), will also appear in the season finale. And we can say "season finale" with confidence, as CBS earlier this week picked up "How I Met Your Mother" for 2006-07.

Acker joined the cast of "Angel" in 2001, playing brilliant but often scatterbrained scientist Winifred "Fred" Burkle until the series ended in 2004. This season she's been playing ruthless spy Kelly Peyton on "Alias."

Although she showed a flair for comedy on "Angel," her appearance on "How I Met Your Mother" will mark her sitcom debut. Her other recent credits include voice work on "Justice League Unlimited" and a guest role on The WB's "Supernatural."