For a little history on this deliciously sublime fake whisky, one need look no further than the two previous sightings which can be found here and here. Strangely enough, the first Glen McKenna sighting is actually the most popular post in the 7 year history of this site. Not too shabby for a scotch which doesn't even exist. The popularity of the Glen McKenna clips on this site are a testament to the connection How I Met Your Mother has to its die hard fan base. It is a show filled with more inside jokes, quotable lines, and drinking game caliber tropes & trivia than any other sitcom in the history of television.
The third and final Glen Mckenna appearance takes place about 10 minutes into episode 3 from the final season. The episode is entitled "Last Time in New York". We are only half way through these sightings. Keep sending in the tips and suggestions.