빼빼로 데이 (Pepero Day) is celebrated on November 11, especially amongst the young people, in Korea. On this day 빼빼로 are given out to friends. I've always understood it as like a "Friendship Day" as I was told. But here are some various versions of its history I found.
1) It was started in Pusan by female students who in the name of maintaining their trim figures, give one another 빼빼로. The shape of 빼빼로 looks like November 11, hence this day being 빼빼로 데이.
Young people give friends 빼빼로 to remind and encourage them to diet and eat 빼빼로 instead of meals to have long legs.
--- me thinks "hahahaha"
2) Ewha Women's University students wanted to be good in their studies and also have long legs, since they are known to have thick legs. So on November 11, at 11.11pm at 11 seconds, they eat 11 빼빼로.
--- me thinks "Aiyo, just because EWU girls are smart, people accuse them of having thick legs.."
3) The company who makes 빼빼로 came up with this day to make lots of money.
--- me thinks "This is the real history! But Lotte denies it..."
The sales of 빼빼로 increase by 70% in November compared to other months!! Oh well, 해피 빼빼로 데이!^^