The gang's at the apartment and we see a title card that says, "eight months ago." Ted and Robin are all snuggly on the couch and SagetTed informs us that back when he and Robin were still dating, they had a joke that only the two of them out of the whole world found funny. Why not put it in a sitcom and test that theory? Barney is arguing with Marshall that March has 31 days. Marshall bellows that it doesn't and that this fact is general knowledge. "General Knowledge," Robin and Ted say in unison, both saluting. Oh man, it's gonna be one of those jokes. I can already see the marks in the soil where it's getting run into the ground. Slide-transition to MacLaren's where SagetTed says the joke continued. Lily is reading an article about corporal punishment. "Corporal Punishment," Ted and Robin salute. Oh, how they laugh. SagetTed says that something like that is really hard to stop. Back at the apartment one night, everybody's watching a movie. Marshall says he has a popcorn kernal stuck in his teeth. "Colonel Stuck-In-My-Teeth," they say. Everyone else is really sick of it. "I hate you!" Barney announces.
The present day. SagetTed says that now that they were broken up, this happened: Marshall is talking about getting a major pay raise. Instead of saluting Major Pay Raise, they just let it slide. Robin and Ted exchange a look. SagetTed says that although it seemed like they were doing well as friends, they really weren't. Being friends with your ex, he says, is hard. Welcome to the corner of Obvious and We Already Knew That, SagetTed. I bet your kids already know it, too. He says you can't be as candid as you once were. In an apartment flashback, Ted is telling Marshall and Barney about a girl in his office who was leaning over. He could see she had a pierced -- he cuts himself off as Robin and Lily are walking toward the front door. Ted awkwardly pronounces Pierce Brosnan to be his favorite Bond. Was it really worth selling out Sean Connery? Was it? Back at the bar. SagetTed says that most importantly, you can never be alone together. Barney's leaving, Marshall is going to pay and Lily is heading to pee. After an awkward moment, Ted says he's going to help pay. Robin's going to help pee.
Ba ba pa pa! (SLAP!) Sorry, just getting ready for it.
MacLaren's. Lily throws a big frozen lump on the table. "We have turkey!" she announces. So why is she dressed like a pauper from Oliver Twist? Lily's excited this will be their first big Thanksgiving together. Like on Friends? Marshall says this is going to be the best Slapsgiving ever. Barney, looking worried, says, "What?" Marshall says it's gonna be the best Thanksgiving ever. Robin says she's invited her friend Bob. You can't invite people to someone else's dinner! Rude! Lily says Robin's only been on like three dates with this guy and they haven't met him. Bob didn't have anywhere else to go. Lily is bent out of shape about it. She thinks 30 years from now, they'll look at photos and say there are the four people they love most in the world...and Bob. Robin says she's "Sore-y" and forgets how seriously Americans take their Thanksgiving. She says real Thanksgiving happened over a month ago. Barney, making fun of her "Sore-y," asks if she just called Canadian Thanksgiving the real Thanksgiving. He asks what Canadians even have to celebrate "aboat." Robin explains Canadian Thanksgiving and I still don't get it, even after years of having very close Canadian friends. As soon as I hear "Northwest Passage" I'm already dozing. Can't you Canadians just cook up a damn turkey and pretend you were founded by pilgrims? And, like, store the turkey for another month? This message brought to you by America: Yes, we are that fucking arrogant. Pass the butter. Barney asks why they're even a country. Dude, I'm sayin'! Marshall says everyone can come over early to watch the Slapsgiving Day Parade. Barney notices it again. Marshall announces that he invented a new holiday: Slapsgiving. Marshall says it's the one day of the year we all get together and (turning deadly serious) give out slaps. Barney starts to sweat.
Split screen: "You guys slept together last night!?" The audience should be on a third screen saying it, too. Everyone agrees it's a terrible idea. Barney announces a "relapse five." You give a high-five, feel awkward, and then high-five again. I like it better when The Todd does these. Lily recaps their recent events of Robin's dating life while she throws in non-sequiturs like, "That is a truth-fact" and "Ka-Blammo." Lily asks why Robin is trying to destroy American Thanksgiving. She says the night before was a fluke. Lily asks if they at least talked about it. Side-whoosh to Robin and Ted getting dressed after sex and awkwardly not talking about it. Back in the present, Robin wants to talk about it. Ted really doesn't. He tries to say that some mushrooms are carnivorous. Probably. Not. They get into an argument about who started the sex. Ted says she "leaned into it" like a Little Leaguer. Ted drops some mushrooms, breaking a dish. "Oh, no! The slappetizers," Marshall says to a rattled Barney. Lily is fed up. She throws Ted and Robin in Ted's room to sort this out. Marshall offers to calm Lily down by putting something on the computer. She thinks it's music, but it's actually the Slap Bet Countdown site. It says 2 hours 45 minutes 20 seconds, but Marshall says, "Look at that! That means we're in the final hour of the countdown!" Barney says he's not scared, but his cheek is twitching. Marshall thinks it's happening because Future Marshall slapped Future Barney so hard that it caused a reverberation in the time/slap continuum. Barney cracks. He cries that he doesn't want to get slapped again. It hurt a lot last time. He doesn't like it one bit. Barney confesses that Marshall made it so much worse with the countdown. He can't sleep, he can't eat, he's lost 10 pounds. He says his suits are wearing him. Barney moves to leave. He says Marshall can slap his face, but he shouldn't be able to slap his mind. Mind-slapping! Marshall doesn't want Barney to go. It's Slapsgiving! Lily yells that it's Thanksgiving. She says it's their first one as grown-up married people. She's mad at everyone. As Slap Bet Commissioner, she rules that there are no slaps on Thanksgiving. "In your face!" Barney yells, "not my face, your face!" Bob walks in, saying hi to his "dudes." Lily tells Marshall her word is final and tells him to go mash some potatoes. Bob brought a bunch of Jell-O shots. "We's gon' get silly, bitches!" he announces. Barney gives him a high-five.