Future Ted: [v.o.] And Marshall and Lily explained. It all started ten years earlier. They had been looking for a new hobby they could do as a couple.
[flashback to Ted wearing winter sports gear in the apartment with a bored Lily and Marshall:]
Ted: I already missed the beginner's lesson. Maybe I shouldn't even go. Ah, screw it. I've seen the Olympics.
I know what I'm doing. I'm going skiing, bitches! [exits]
Lily: He's gonna break his leg.
Marshall: He's not gonna break his leg.
Lily: 20 bucks says he does.
Marshall: "Lily bets Marshall that Ted will break his leg skiing." [they shake hands]
[12 hours later, Ted's entire upper body is in a cast and he's wearing a neck brace:]
Ted: You would be amazed. People fall off ski lifts all the time. Well, I gotta hit the head.
Lily: Well, he didn't break his leg. [gives Marshall money]
Marshall: Yeah, I gotta say that, um, making money off this bet just makes me feel...
Lily: More alive than you've felt in years?
Marshall: Yes!
Lily: New hobby!
Marshall: We need a cash box, some glitter and some glue!