'The Magician's Code - Part Two' - Season 7, Episode 24
On Barney's future wedding day, when his wife is finally revealed, the gang reminisces about the time they encouraged Ted to follow his heart and go after the one that got away, on the second part of the one-hour seventh season finale of How I Met Your Mother.
Air Date: May 14th 2012.
Security Guard: (referring to the metal box counting down) Is that thing going to blow up?
Barney: (loudly) What?