After nine seasons, the final episode of How I Met Your Mother airs in the United States on Monday, March 31. Curiata.com is reliving the series this week by looking back at our favorites of the 208 episodes.

Chuck Cunningham and Judy Winslow vanished. Cory Matthews aged three years in one season. Jerry and Elaine dated for one episode and it was never mentioned again. Sitcoms are notorious for shaky continuity. Perhaps the writers believe these fictional characters only exist to make us laugh, so continuity should be no issue.

But How I Met Your Mother shows us why continuity is important. Besides creating an amazing narrative story that transcends the simple sitcom formula, it also creates a web of jokes that make the show appreciably better to longtime fans. Many shows make callback jokes, but rarely does a show dedicate an entire episode of its final season to a gag started seven years prior. And no show has done it in a way that feels relevant quite like How I Met Your Mother.

The perfect example of this is the season 2 episode, alternately called “Slap Bet” or “Robin Sparkles,” the second title originally being dropped to withhold the secret reveal. The two different titles give away exactly why the episode is so important. It created two strong running jokes that would be referenced straight through to the finale.

Spoiler alert! Robin Scherbatsky was a Canadian pop star in the 90s. And an awesome one at that. She even rapped.

The Robin Sparkles reveal is one of the funniest moments in any sitcom. “Let’s Go to The Mall” was my ringtone for a time. And who can forget all of the later jokes this reveal spawned? There was the time when Robin Sparkles made mathematics quite erotic. Alan Thicke certainly enjoyed it. Then there was the absolute classic Behind the Music joke about Robin as Alanis Morissette, including, surprisingly, the first Full House reference, when Dave Coulier made his always-awesome “cut it out” joke. None of these late series jokes would have been possible without the foundation laid out in season 2.

Then, of course, there is the Slap Bet. After a series of events involving a wager over Robin’s past, Marshall gained the right to slap Barney five times, any time, for the rest of their lives. After gaining three at a later date, Marshall ended up with eight slaps, often doled out in episodes dedicated entirely to the impending slap. Remember “Slapsgiving”? Or “Slapsgiving 2”? Or “Slappointment in Slapmarra” from the final season? Maybe it’s best we don’t remember much from the final season, except for the final slap, delivered to Barney at the altar on his wedding day.

Even without acknowledging the later impact of this episode on the series, the episode is fantastic in its own right. The episode showcases the comedic gold-mine combination of Marshall and Barney, while going far in establishing who Ted and Robin are as individuals and as a couple. Robin’s reserve conflicts harshly with Ted’s openness about who he is. It’s difficult for Ted to accept the secrets Robin wants to keep, though his goodhearted side ultimately wins out, and he accepts her decision. Robin, too, grows, deciding that her past should be known by the people she loves, no matter how terrible, or bubblegum pop-ish, it is.

Continuity is difficult to maintain, but when done right, it can create a rich history to build upon and add anticipation to the big moments of the show. How I Met Your Mother has mastered this craft and I’m sure the finale will show us why it’s been worth the ride.

Best Line:
Ted: You’re afraid of the seven dwarfs?
Robin: Just Doc. He’s creepy. I mean, he’s got a medical degree. Why is he hanging around a bunch of coal miners?

Best Cutaway:

Mother Lore: None.