What is Slapsgiving you ask? How I Met Your Mother is my favorite show on TV and a couple of years ago there was a Slap Bet. A Slap Bet is the ultimate bet...the winner gets to slap the loser as hard as they can with an open hand across the face.
When Marshall won this bet, he was given the option of slapping Barney 10 times in a row immediately, or 5 times of his choosing. The third of these slaps was delivered on a Thanksgiving that Marshall renamed "Slapsgiving" and it was an entire episode where Barney knew it was coming and was a nervous wreck with anticipation. The fourth slap was delivered on the following "Slapsgiving: The Revenge".