UPDATE - 2/2@4:08PM: On Thursday Hypable.com broke down the first promo video for the show that reveals some details about the episode's premise:
... The promo promises that we'll see how the Canadian teen sensation Robin Sparkles went from pop princess to queen of darkness! The episode will show us a mockumentary showing Robin's fall from grace, which will include appearances by a lot of big name Canadian stars.
The episode will feature James Van Der Beek, Jason Priestley, Alan Thicke, Paul Shaffer, Alex Trebek, K.D. Lang, former Barenaked Ladies frontman Steven Page, Rush frontman Geddy Lee, and former Canadian hockey player Luc Robitaille. ...
Then today they released another promotional video showing clips from the mockumentary show mentioned above. The show is a take-off on VH1's Behind the Music called Underneath the Tunes. The promo talks about the day when the dark side of Robin Sparkles was revealed, and depicts Geddy Lee at about the 15-second mark saying, "a little piece of Canada died that day". You can watch the promo below or on YouTube at this location (thanks Mark):
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UPDATE - 1/11@9:36AM: It looks like Geddy filmed his spot yesterday based on this photo that Rush posted to their Facebook page last night.
The Huffington Post reported earlier this evening that several Canadian stars including Geddy Lee will make a guest appearance on the February 4th episode (Season 8, Episode 15: P.S. I Love You) of the CBS sitcom How I Met Your Mother:
"How I Met Your Mother" is trotting out some very big Canadian stars for the return of Robin Sparkles on Monday, February 4. Alan Thicke, Alex Trebek, K.D. Lang and James Van Der Beek are just a few of the stars who will appear in the episode marking the return of Cobie Smulders in her Canadian pop star guise.
The full list of stars appearing on the show are listed in a video accompanying the article. How I Met Your Mother airs Monday nights at 8PM EST on CBS. One of the stars of the show is Jason Segel who also starred in the 2009 film I Love You Man where Rush made a guest appearance. Thanks to Steve B for the heads up.