Self-PortraitistsBruno Mars, Snooki & More Celebrity Twitter Pictures (Photos)Idol’s Randy Jackson hangs out with Justin Bieber, Snooki’s fashion, and more stars’ Twitter photos.Anna Klassen01.29.12 4:45 AM ETJamie Lynn Spears dancing in a cowgirl get-up, Bruno Mars with an even wackier hairdo, Christina Aguilera harmonizing with the late Etta James, and Justin Bieber hanging with American Idol’s Randy Jackson. Plus, more celebrity Twitter pictures from this week. Jonah HillJonah Hill has had a terrific year. His role in Moneyball garnered him an Oscar nomination, and we can’t help but be impressed with his new, slimmer physique. Getting back to his comedic roots, Hill tweeted a photo of himself in front of an advertisement for 21 Jump Street, which costars Channing Tatum, and wrote, “21 Jump Street. March 16! It's beginning.” Emmy RossumEmmy Rossum tweeted this photo of herself with Hollywood's most famous canine, Uggie from The Artist, and wrote, “Holy moly. I'm starstruck. Dogstruck. This is me and Uggie, from ‘the artist’!!!!” Jamie Lynn SpearsJamie Lynn Spears has slipped under the radar since the birth of her now-3-year-old daughter, Maggie. But let’s hope Mommy Spears had a babysitter when she tweeted this picture of herself dancing at a cowboy-inspired party. She wrote, “Thanks @cowboytroy for teaching me some solid dance moves at @johnrichbday party!! #goodtimes.” Lea MicheleIn her recent Candie’s campaign, Lea Michele bares more skin than her family-friendly character Rachel Berry on Glee. Hanging out with fellow Gleek Chord Overstreet, she tweets this photo of the star taking a bite out of an apple and writes, “Watching @chordoverstreet eat an apple right now and wow trouty mouth can take some huuuge bites!!!! Haha.” SnookiSnooki, er, Nicole Polizzi, tweeted this photo of herself in chunky black-and-white-striped heels, a black mini, and a lime cheetah-print jacket, and wrote, “My style ;) gaudy tacky and extremely out there.” We can’t argue with that. Christina AguileraLast week marked the passing of blues legend Etta James. Her death was felt all over the music industry, and Christina Aguilera tweeted this black-and-white picture of herself singing with James in 2010. She wrote, “One of the greatest moments of my life ... Singing with my idol, the legendary Etta James. You will forever be missed.” Ricky GervaisAnimal activist Ricky Gervais has been retweeted by @PETA a number of times, so it came as no surprise to see the animal lover tweeting this pic of himself with a small, furry creature, reminding dog owners to “collar a dog, spread the word, help save a life”. WhoSay.com / Randy JacksonRandy JacksonRandy Jackson, the only original American Idol judge left on the show, tweeted a photo via his WhoSay account of himself with a cheetah-print-clad Justin Bieber and wrote, “My boy @justinbieber stopped by to say hi, check out his vest!” Katherine HeiglKatherine Heigl, who appeared in the critically despised ++New Year’s Eve late last year, can now be seen in One for the Money, based on the book by Janet Evanovich. Heigl tweeted this photo of herself with the author at the New York premiere of the film and wrote, “Finally, the coolest author, the very brilliant @janetevanovich.” Jimmy KimmelJimmy Kimmel was looking exceptionally hungry when he tweeted this photo of himself about to bite into a giant meatball. The late-night TV host was apparently trying out his hand at cooking when he wrote, “thanks to @MEATBALLERS for the 9th anniversary celebratory meatballs — great cookbook!” Bruno MarsBruno Mars had a dose of food poisoning that threatened to stop his performance in Rio. But the show must go on, so Mars and his signature pompadour performed as scheduled. The “Grenade” crooner tweeted these photos of himself with two very different, but equally memorable hairstyles, and wrote, “Side Show Bob Vs La Bamba #BattleOfTheDoos.” Kelly OsbourneKelly Osbourne sports a silvery, almost lavender hair color in this photo she tweeted of herself and two friends. “chungalexa's photo team evil reunite!” she wrote. But the new hue isn’t likely here to stay. "I can't keep bleaching my hair and I want to grow it so I take breaks in between. I did it a year ago but it was more of a lavender gray, but I went straight gray this time,” she told Us Weekly.