There are only two episodes left until the highly anticipated series finale of "How I Met Your Mother." The countdown will continue on Monday with an all-new episode in which Gary Blauman will show up minutes before the wedding and send the gang into an uproar.

In the upcoming episode, aptly titled "Gary Blauman," Taran Killam will reprise his role as Gary Blauman and Wayne Brady will return as Barney's brother James, reports CarterMatt.

In a video teaser, Barney is seen punching a hole in the wall and at an utter loss of words at one point, while Robin is seen freaking out in her wedding dress.

CBS issued an official synopsis for the show that states: "When Gary Blauman shows up at the wedding, it is going to send the gang into a frenzy as they each recall an encounter with him."

Other guest stars in Episode 21 include Emily C. Chang as Steph, Joe Nieves playing Carl, and William Zabka as himself, notes the Hollywood Hills.

As "How I Met Your Mother" moves towards its series finale on March 31, speculation has been rampant that Ted's expected bride-to-be has been dead the entire time that he has been narrating their first encounter with each other.

However, Cristin Milioti recently dispelled rumors that her character, The Mother, is dead in an interview.

"That's insane," Milioti told The Hollywood Reporter after learning that some fans believe that The Mother is not alive. "There are some crazy conspiracy theories, which really makes me love the fans more... That is so crazy," she added.

Milioti also went on to call the finale "beautiful," noting that no alternate endings were written or filmed. "They've had this vision for nine years, and it's in great hands," she says referring to co-creators Carter Bays and Craig Thomas. "They know exactly what they want to do."

"Gary Blauman" is set to air on Monday, March 17, at 8 p.m. EST on CBS.

Watch a preview below.

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