Flash back to a tipsy Robin. Her hair is in two pigtails, and she's wearing a Canucks jersey (#1: Luongo), hockey gloves and wielding a stick. "Stanley Cup. Game 6, eh? The Rangers are aboat [not about, not aboot] to be sorry they ever played shinny with the Canucks." Marshall opens the apartment door and offers Robin 20 bucks if she can shoot the puck through it. Robin laughs. "Oh-ho, you're nuttier than a Tim Hortons Maple Log!" She shoots! She scores! Okay, no. She shoots and the shot is flying straight at the wall, but Lily, who is wearing oven mitts and an apron, comes out from the kitchen and catches it, and orders Robin to give her the stick. Robin says, "I'll give you summer teeth. Some are here. Some are there." She's a nasty little drunk, isn't she? The guys laugh, while Lily tries to get the stick away from Robin, who shoves her away. "Take off, hoser." Lily's had it. And the gloves (or oven mitts, in Lily's case) are off! They scrap and Lily gets the stick from Robin and throws it down. Then the fight heats up. In the background, Marshall cheers, "For America!" which for some reason makes me laugh so hard I have to rewind to hear the rest of the scene. Ted finally breaks it up -- the fight, not my laughter (well...) -- and Barney recoils as if in pain. "Ted, no! You never break up a girl fight! Never!" He punches the wall, smashing his hand right through and leaves the apartment in a fury. Back in the present, Ted tells Marshall that was entirely Barney's fault, as was the big scorch over the fireplace.
The story of the scorch mark over the fireplace needs the backstory of the gang's introduction to the practice of intervention. Remember Stuart -- who married Claudia? After they were married and Claudia went brunette, all Stuart's friends gathered to confront him about his alcoholism (of course Barney misread the Evite and brought a bottle of booze). Soon, our gang is so addicted to intervening; they make an "INTERVENTION" banner, and hold interventions any time one of them does anything the rest of them don't like -- Marshall wearing his Cat In The Hat hat all the time; Lily adopting an English accent that's bollocks; Robin's spray-tan compulsion; and... Barney's magic tricks.