How I Met Your Mother, the slow-burn CBS comedy that turned into a somewhat unlikely hit before wrapping up tonight, also became a social-media power in recent years, setting up tonight’s finale episode as occasion for yet another online blizzard of goodbyes.

Related: ‘HIMYM’ Finale Outrun By Social Media

HIMYM Farewell Mosaic page screen cap
HIMYM Farewell Page

CBS has encouraged that sort of growth with a series of clever fan interactions, like sprinkling photographic clues on Facebook about the identity of the mother in last season’s run-up to her big reveal episode. Just after the episode ended, CBS posted a followup, with the hashtag #WeMetTheMother, that reached 13 million people on Facebook, according to the network.

Related: Cobie Smulders Talks ‘HIMYM’ On Letterman: Video

This year, ahead of the finale, the company launched a hashtag on its own website, #HIMYMFanFarewell. Fans were asked to post farewell messages to the show using that hashtag on Facebook, Twitter, Vine and other platforms. Then the company aggregated a mosaic of those posts on a (sponsored) page on Check it out. It’s an interesting gimmick, and the car sponsorship that’ll pay for it all is a smart thing too.

Related: ‘How I Met Your Mother’ Gains Ratings Momentum

The network also set up a “guestbook” page for last week’s wedding episode, so fans could RSVP for the wedding and leave their well-wishes for the couple. The network says it’s all paying off with better ratings this last season, up 3 to 4 percent in overall and younger demographics (it’s the network’s youngest-skewing show). And online streams of the show on are up double digits this year, though the network didn’t specify by how much.

HIMYM 3seasons Social Media graphic

And this isn’t just the network bragging here. We checked in with our friends over at RelishMIX, an independent consulting firm that analyzes fan social-media engagement through Twitter, Facebook and YouTube with TV shows and movies. In its last three seasons, HIMYM’s fan engagement online jumped nearly 85 percent across the Big Three social-media sites, according to RelishMIX.

Perhaps just as interesting has been that the biggest source of engagement each season has come from a different social-media site, according to RelishMIX. This year, as the show wrapped up its nine-year story line, social-media growth continued too. During the season, the show added another nearly 9 million in online reposts, likes, fan videos and shares. RelishMIX CEO Marc Karzen called that “good but not great,” especially in comparison with CBS’s two Chuck Lorre-produced comedies, The Big Bang Theory and Two and a Half Men. Both shows are online powerhouses whose numbers have “dwarfed” HIMYM, says Karzen.

For its part, CBS says the show’s “overall social conversation,” as measured by another firm, SocialGuide, is up  42 percent this season, 43 percent on Facebook.

HIMYM Twitter finished tableThe show’s interactive strength has certainly been boosted by its cast members’ big online presences, led by Neil Patrick Harris and Jason Segel on Twitter. Three other cast members – Cobie Smulders, Alyson Hannigan and Josh Radnor – have at least 470,000 Twitter followers each, as does the show’s official Twitter feed. By comparison, Two and a Half Men continues to benefit greatly from the presence of Ashton Kutcher (@AplusK has nearly 16 million Twitter followers, double even that of the redoubtable Harris).

The story is similar on Facebook, though it’s mostly driven by the show’s own site there, with help from Radnor, Smulders and Hannigan. Not bad for a little-heralded comedy that barely made it through three seasons before catching fire.

HIMYM Facebook finished chart
Note: Links here aren’t live. Click on the chart to go to CBS’ Facebook page for the show.