It’s Britney, bitch! Underneath those unkempt extensions is still a pop superstar whose every effort reigns atop the charts. Since “Hold It Against Me,” the first single off her yet-untitled album, was digitally released on Monday, it’s already shattered all previous records for the most first-day airplay, and shot to #1 on iTunes.Produced by Dr. Luke, it’s a bass-heavy dance gem featuring Britney doing what she does best: delivering groan-worthy double entendres in her trademark sexy, nasally voice. If you’ve yet to hear Britney’s latest, you can check it out here. Or you could just hit Neighbours’ dance floor this weekend.