That’s because two Whedonverse stars are on the show. Vincent Kartheiser (Pete) was a major character (Connor) on Angel season 4 (and had guest appearances in season 5), and Christina Hendricks (Joan) had major guest shots on Firefly as Saffron, and a small (tiny) part in Angel season 1 as an Irish barmaid.
What Whedonesque failed to mention, but Roberta’s eagle eyes noticed, was Adam Kaufman, who played Bob Shaw, the air-conditioner salesman who penetrates Betty’s imagination in Indian Summer. He played heartbreaker Parker Abrams in Buffy’s fourth season.
Coolest of all to the lover of detail is Andy Umberger, who is Betty’s shrink, Dr. Wayne. He has appeared on all three of Joss Whedon’s series, on Buffy as D’Hoffryn, who is Demon in Charge of Vengeance Demons (a tough job with major seniority), on Angel as Dr. Ronald Meltzer (a seriously creepy one-off villain in season 1) and in a small role on Firefly as captain of the Dortmunder in the pilot.