The Austin Powers actor will be reunited with his former Buffy co-star Alyson Hannigan in an upcoming episode of the sitcom, TVLine reports. Green will play Daryl LaCoutre, an old college friend of Lily (Hannigan) and husband Marshall (Jason Segel). While Daryl considers the couple to be close friends, they barely remember him and he soon becomes obsessive in his efforts to spend time with them. In addition to playing Oz - werewolf lover of Hannigan's Willow - on Buffy the Vampire Slayer, 38-year-old Green is known for voicing Chris Griffin on Family Guy and for co-creating Adult Swim series Robot Chicken. His How I Met Your Mother episode is currently scheduled to air on December 10.