Episode 31 of "How I Met Your Mother"
s02e09 Slap Bet
Title: Slap Bet
Original Air Date: 11/20/2006 on CBS
Plot Outline:
Barney uncovers Robin's secret past and the real reason behind her strong aversion to malls. Curious about Robins distaste for shopping malls, Barney does some digging and discovers her hidden past. When he unveils the embarrassing truth to the gang, they cannot believe what they see and hear Robin doing and are provided with endless hours of amusement from their new discovery about her teenage years.
