I can't believe no one else has said it...
The Spice Girls! I used to love the Spice Girls for like 6 months I was a *huge* Spice Girl fan. I even got one of those "Girl Rules" shirts, the toys, a CD, and the movie was like my favorite. Plus I was the only person that wanted to buy the Spice Girl video game.
I admit it >_>; Not that I think the Spice Girls are horriable (They are ok, I think) but OH GOD @__@ I can't believe how much I liked them...