Ievan Polkka (Eve's Polka) is a song originally sung by Finnish band Loituma which gained popularity as a Vocaloid cover song among Vocaloid fans. The song shot to fame due to the popular internet meme (called Leekspin) of Orihime Inoue from the Japanese manga Bleach twirling a negi to an infinite loop of the 5th stanza of Ievan Polkka.
The first Vocaloid to cover the song was by Miku Hatsune under the alias of Miku Hachune of which this song was her first appearence. Since then there have been countless other covers by the other vocaloids including solos, duets and even a quartet mimicking the original.
The Cover and video was made by Otomania and it was Illustrated by Tamago. It is one of Miku's popular cover song,which stars Miku Hachune (はちゅねミク), who is a blank-eyed doll-like chibi version of Miku with a gaping mouth that waves a negi in time to the music. This video also solids Miku's Item War.
Consequently, Hatsune became known for having a leek in her hand and her fame for the video outshone Inoue, and as a result, when viewers spotted the 'Leekspin' reference in Phineas and Ferb, they credited the reference to Miku and not Orihime.