How I Met Your Mother is set to stage a Buffy the Vampire Slayer reunion.

The CBS sitcom announced via Twitter today that Seth Green (who appeared on that cult favorite opposite Alyson Hannigan) will guest star on an upcoming episode as Daryl LaCoutre, a college classmate believed back in the day that Lily and Marshall were his best buds.

But when this married couple comes across the character 12 years later, awkwardness ensues when they scarcely recall anything about him.

Hannigan and Green portrayed the on-screen couple Willow and Oz for nearly three seasons on Buffy the Vampire Slayer.

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.