'Cause one of my online friends told me as soon as I ordered my first Pop'n game: "Check out Zizz's song on youtube. Its something youll like!" So I did.
100 sec Kitchen Battle. That song was brought to my attention after a friend tried out Popn 10 AC at the arcade I frequent. Candy was the most popular song on the cabinet at the moment but I didn't really like it even on DDR. So I decided to play everything else. What really sold me to Popn was JACK. That song is MARVELOUS. XD
Linus have a part too. I lurved that song in IIDX 6th, then I saw someone play it in the arcade. Crazy stuff. Even after so many years now I can't pass it frequently.
No particular song introduced me. I randomly decided to import a few games (1-3 for PSX) in 2001. I started with pop'n music 3 because it was the newest I had, and the first song I played was Take me to... (G-POP)
I failed pretty miserably, but being the persistent type, I kept at it until I beat it. The music didn't really grab me in particular, but the gameplay was pretty fun so I kept up with it all.
The first I had heard of Pop'n Music was the Classic 4 video, but playing the 4 Pop'n songs on DDR and hearing some of the songs from Pop'n 9 AC also influenced my decision to start importing the games.