Ep 9. Slap Bet

In How I Met Your Mother season 2 episode 9 titled "Slap Bet," the gang is consumed by a bet over Robin's mysterious past. Barney has created the slap bet, allowing the winner to slap the loser across the face as hard as they can. Marshall and Barney wager on two possible scenarios - whether Robin was a secret pop star or a character in a Canadian porn movie.

Lily is then appointed judge and tries to get to the bottom of Robin's secrets. Meanwhile, Ted tries to avoid getting involved, but eventually gets wrapped up in the bet. As the episode progresses, both Marshall and Barney begin to gather evidence to support their respective bets. With the help of their friends, they try to uncover Robin's past in any way they can.

In the end, the group finally discovers the truth about Robin's past. The slap bet winner is declared, and the losing party is subjected to a painful slap across the face. With this episode, the audience gains a deeper understanding of the characters and their relationships with each other. The slap bet creates a sense of competitiveness and humor among the group, revealing their playful and lighthearted sides.

"Slap Bet" has become one of the most iconic episodes of the series due to its humor and memorable moments. It has been recognized as a classic episode among fans and has even appeared on various "best of their sitcom" lists. The episode perfectly blends comedy and mystery, making it one of the most popular episodes in How I Met Your Mother's nine-season run.