"How I Met Your Mother" season 9 has only 2 more episodes left before the finale! New spoilers reveal that Taran Killam guest stars in episode 21, and Barney and Robin will freak out when he appears before the wedding in "How I Met Your Mother" season 9, episode 21.

Watch the promo video below!

The synopsis for "How I Met Your Mother" season 9, episode 21, titled "Gary Blauman," reads: "When Gary Blauman shows up minutes before the wedding is about to begin, it sends the gang into a frenzy as they each recall an encounter with him."

Taran Killam will guest star as Gary Blauman in next week's episode, while Wayne Brady will return as Barney's brother James, Hollywood Hills reports.

The promo video reveals that Barney and Robin will lose it when they see Taran Killam's character Gary - Barney punches holes in the walls, and Robin has a meltdown! This episode is sure to send the gang into "Code red!" mode before the wedding begins.

Fun fact: Cobie Smulders (who plays Robin) is married to Taran Killam! They married in September, 2012 and have a daughter together. 

"How I Met Your Mother" season 9, episode 21 is scheduled to air on Monday night, March 17 at 8/7c on CBS.

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