Miley Cyrus turns 21 today — happy birthday, girl! — and we're celebrating by turning over our entire network to her, for an 8-hour b-day bash that includes the premiere of a brand-new special: "21 Candles: Miley's MTV Moments," where she looks back on her most memorable performances, videos and interviews.

"21 Candles" premieres at 12 p.m. ET/PT, and immediately following that, we're presenting the extended-cut of her MTV doc, "Miley: The Movement — Deluxe," featuring commentary from the birthday girl herself!

She'll be revealing secrets of key moments from "The Movement" ... and we can't wait to hear what she has to say about these bonus scenes, taken from the "Deluxe" version of the doc.

"Yeah, I'm That Bitch!"

Sure, most folks only remember Miley's onstage moment at the MTV Video Music Awards ... but before she shocked, she rocked baubles and baby buns on the red carpet. And, here, we learn that it wasn't a stylist who selected the outfit, it was her pal Pharrell, who was very interested in helping Miley channel her inner "Bad Bitch."

"My stylist was irritated with me. I picked out what I was going to wear on the red carpet this year because I want to be like, 'Yeah, I'm that bitch, I picked out what I wore, I went shopping with Pharrell, and this is what I bought," Miley says. "That outfit, I feel like again that's something that separates me, because no other girl is like, 'I went shopping; this is vintage; this is one of a kind, this is from the year I was born.' I went shopping with Pharrell when I started working on my record, it's come full circle."

"I'm A Freak"

Speaking of that VMA performance, "The Movement — Deluxe" gives us an exclusive look at the closed-set rehearsals that led to Miley's tongue-and-twerk epic. Backed by a band (and wearing unicorn slippers), Cyrus works through her steps, while Robin Thicke looks on bemusedly. And while the two crack jokes throughout, Miley is very serious about delivering a performance that will have people talking.

"This is when you get to do something fun. I'm a freak. I want to come out of a teddy bear for Christ's sake — with a [foam] hand — I'm just a freak," she tells Thicke. "I don't think it's that I'm smarter than anyone else, it's not that I think, 'Oh, you don't get it.' It's just who I am and if I'm gonna perform, I want things around me that I like."

"I Don't Give A Sh--If People Like Me"

While shooting her down-and-dirty VMA promo clip, Miley breaks down the mantra behind Bangerz. Simply put, she doesn't give a sh-- what people think, she's making music for her, and her fans. Because whether you like her or not, she knows you're going to be talking about her.

"I don't give a sh-- if people like me, I just want people to respect me and what I'm doing ... I'm used to people judging me; I'm used to people knocking me down; I'm used to getting back up. I don't feel scared like that," she says. "I just want to be myself. I'm going to control what I do; what I do is meant for my fans. It is so important. Everything I do is going to be talked about, so it has to be on that same page."