Leekspin

leekspin is a swf file from some time in 2006. In the loop, an anime girl (Orihime Inoue from Bleach) spins a leek. The clip of music in the swf is from Loituma's Ievan Polkka. Loituma, a Finnish band, was made known to outsiders and became quite popular locally due to leekspin's popularity.

As stated above, the Flash loop appeared some time in 2006, which is around the time when pretty much anything interesting happened in regards to 4chan.