Ted's room. Robin whines that they can't be together. Ted says they aren't really friends. They avoid each other, smile politely. He says they only pretend to be friends because it's convenient. Robin wonders if they should stop pretending. "Maybe we should," Ted says. They agree to go eat dinner, then that's it. They're both sad. Robin leaves. "Happy Thanksgiving," Ted says.
Dinner, later. Everyone is sitting together. Barney asks if Marshall's "Slappetite" was ruined. He thinks Lily might want to say a few words. "Nope. This sucks. Eat up and leave," she says. Marshall stands to give a toast. He says Lily did something great by starting a new tradition. Marshall says they're going to do this every year, maybe for the rest of their lives. Ted and Robin exchange looks. They're trapped! Everybody toasts. "This is rad!" Bob says. He talks about his family and how with 10 kids, his family is always chaotic at Thanksgiving. He says it's a major buzzkill. "Major Buzzkill!" Ted and Robin announce. Everyone thought they were done with that. Apparently they aren't, Ted and Robin agree.
Montage of happy eating. SagetTed says that friendship is an involuntary response. He says it was a wonderful dinner with four people he loves and with Bob. It did become a tradition. He says that's why they go to Lily and Marshall's every year for Thanksgiving. Barney busts out the laptop and shows the countdown. He says it's the last 20 seconds, counting down to nothing. Lily tells him to put it away. Barney stands, taunting Marshall, asking how it feels to be so impotent, his large flaccid hand dangling in the wind. The countdown starts rattling off the numbers out loud. Barney continues taunting. Lily, mad, tells Marshall he can slap Barney. Marshall, giddy, stands and slaps Barney. Barney spins and lands on a tiny end table, flattening it. Everybody laughs. "That's three!" Marshall announces. He's composed a song for the occasion. Ted adjusts the lights. Marshall goes to the piano. It's pretty and slow. And funny. Marshall sings: "What is this feeling that's put you in your place? A hot, red burning on the side of your face." Barney sits on the floor, rubbing his cheek. "You feel the blood rush to your cheek. Tears start to fill your eyes. And your lips are trembling, but you can't speak. You're trying, oh, you're trying not to cry. You just got slapped!" Barney sings: "Oh, oh!" "Across the face, my friend!" Barney: "Oh, oh, oh!" Marshall: "You just got slapped!" Barney: "Whoah, oh, oh, oh, oh!" Marshall: "Yes, that really just happened!" Barney continues with the "Oh, oh, oh, ohs." Marshall: "Everybody saw it. And everybody laughed and clapped." Ted and Robin hold up lighters. Bob holds up an open cell phone. Marshall: "It was awesome. Wait, you just got slapped." Barney holds his cheek. Best song ever. Right up there with "Slap On You Crazy Diamond." "Happy Slapsgiving, everybody," Marshall says.