Mo Ryan posted this nerd-tastic news on her BSG-lovin' blog,
The Watcher:
"I can exclusively reveal that Katee Sackhoff, formerly Kara "Starbuck" Thrace on "Battlestar," will have a small role in the Nov. 23 episode of "Big Bang Theory.""
The article is
here, and does contain spoilers at the bottom of the post (clearly labeled) about her character. It looks like it's going to be legendary.