#HIMYM, Season 9 Episode 21
Episode 21 "Gary Blauman" aired on march 17 - 2014.
When Gary Blauman shows up at the wedding, it sends the gang into a frenzy as they each recall an encounter with him. Since Robin didn't know he was coming to the wedding she goes to Marshall for help with a place.
Gary Blauman is acually played by Cobie Smulders' real life husband Taran Killam who acually is the center of the story for most of the episode.
We also get a quick look at some of the other people that have been part of the story through the 9 seasons. People like Carl the Bartender, Steve The Blitz, Kevin (Robin's ex boyfriend/therapist) and a few others.
The epsiode starts with this ...
And we get to see Ted and the mothers first date as Ted tells her the story about Blauman.