It's called 'Slap Bet'. It aired originally on November 20, 2006. You should be able to watch it on watchxonline.com (the link is on the bottom of this page)
it's from the episode called Slap Bet in Season 2
Season 2, Episode 16, "Stuff." To irritate Lily, Barney puts on a one man show. At the end of the episode, it was clearly so irritating to Lily that Marshall delivers his second slap as a part of their slap bet.
Slap Bet was created on 2006-11-20.
A slap bet!
Season 4 episode 12The One With The Embryos
How I Met Your Mother - 2005 Slap Bet 2-9 was released on: USA: 20 November 2006 Australia: 5 April 2007 Hungary: 15 December 2008 Germany: 3 January 2009 Netherlands: 2 June 2009 Japan: 10 October 2010
In the Halloween episode of the TV show "How I Met Your Mother," Marshall has made a bet involving a homemade costume with Barney involving Lily's sex dreams. Turtle is Barney's costume for the bet. Barney ultimately loses the bet and has to wear the costume for a year.
"Let's go to the mall" comes in the same episode as the slap bet between Marshall and Barney is made, season 1 pal ;-)
Not Gonna be able to do it by double x
I think it was season two, the BET BET BET episode where Fred has the gambling problem. He made a bet with Arnold and lost.
No, but if they did I bet it would have to do with Nevel.
"im not gunna be able to do it" double xx posse