They may seem sweet, but behind the scenes, these stars are downright nasty!
Click through the gallery below to check out our round-up of the 20 meanest celebs in Hollywood — you may be surprised:
20. Julia Roberts: She may be known as America's Sweetheart, but the Oscar-winning actress wasn't so sweet to her own family. Julia reportedly treated her troubled half sister Nancy Motes so cruelly that the woman committed suicide in February. Plus, during a recent photo shoot. "Julia hated one of the dresses chosen for her model. Instead of simply explaining it to the stylist, she took the dress and threw it across the room," claims a source. "When the stylist went to retrieve the item, Julia screamed, 'Don't f---ing bother!'"
19. Christina Aguilera: How dare you shop in the same store as Christina! When the 'Voice' mentor recently went shopping at a gag-gift store on Sunset Boulevard, she turned the whoopee cushion patrons into prisoners! "As soon as Christina entered, she requested that the doors be locked so no one could leave or enter," a fellow shopper tells Star. "The rest of the customers had to wait until she was completely done before we could leave. And while we were on lockdown, Christina laughed when asked to sign autographs or take pictures. We couldn't wait to get away from her!"
18. Josh Duhamel: The handsome hunk is extremely controlling and jealous of his wife, Fergie. "He monitors her every move and gives her a hard time when she wants to hang out with friends," says a source. "Josh flips if there are any guys he doesn't know around her. He is downright rude and mean-spirited to her pals." Josh even tried to get Fergie to leave the Black Eyed Peas because he hates that she's around male bandmates. "The truth is: he puts on a cocky front, but his controlling behavior is a result of insecurity," the source adds. "He's one of the most insecure men around."
17. Kristin Cavallari She became famous as a high school mean girl on 'Laguna Beach,' and apparently age hasn't calmed the new mom down. At a recent event, a starstruck fan approached Kristin, asking, "I love you so much. Can you sign something for me?" As the fan dug in her purse for a pen, Kristin "rolled her eyes and made a face mocking the girl and then snickered," a witness tells Star. Talk about two-faced!
16. Jared Leto: In March, Star reported how the Oscar winner and lead singer of 30 Seconds to Mars grabbed a stripper's throat during a lap dance and told her he could "reach pure sexual enjoyment in 30 seconds just by looking at your eyes." And it seems his threatening brand of flirtation is rather common. "He came up to me at a party in Malibu and asked if I liked giving oral sex. I was speechless, and he said, 'Why don't we go inside and you can show me,'" a source tells Star. "As I was walking away, he commented on my 'juicy butt!'" That's not very gentlemanly behavior, Jared!
15. Naya Rivera After a whodunit worthy of Agatha Christie, 'Glee' star Naya Rivera became the prime suspect in a smear campaign against her hated costar Lea Michele. It turns out that it was Naya, not Lea, causing problems on the set of the show, which is why she was written out of the series' final episodes. Now Naya is freaking out about getting her next job. "People in the industry are finding out she has a sour attitude," an insider says.
14. Sandra Bullock: Everyone seems to love Sandy, but the feelings are not mutual. Star first reported in 2012 how she screamed at a wheelchair-bound veteran who asked for an autograph on the set of 'The Heat.' Sandra denies the incident ever took place -- but on a recent red carpet, a reporter asked her a standard "What designer are you wearing" question, and Sandra responded ,"How could you ask such a stupid question?" humiliating the reporter in front of a room full of people. Lighten up, Sandy -- even Star reporters aren't made of stone!
13. Charlie Sheen: The bad boy has gone after pretty much all of Hollywood, tweeting: "I'm the King u [Ashton Kutcher] r a jester" and comparing meeting Rihanna to, "84 interminable seconds of chugging Draino."
12. Rihanna: After a 16-year-old posted her prom dress, which was inspired by Rihanna, the pop star responded by Instagramming a frowny face and compared the poor girl to a bat.
11. Kanye West: Jimmy Kimmel poked fun at Kanye, causing the rapper to start a Twitter war, writing: "YOU CAN'T PUT YOURSELF IN MY SHOES... YOUR FACE LOOKS CRAZY... IS THAT FUNNY?..."
10. Kirstie Alley: After Leah Remini left scientology, Kirstie let loose, tweeting, "When faced w malicious gossip I take a moment to experience the loss of the person I thought was my friend...Then I say f--- 'em..."
9. Joan Rivers: The comedian kicked Lindsay Lohan when she was on trial in 2010, saying the actress was "so dumb" that "her idea of being sworn in is cursing in front of a judge."
8. Madonna: She's never pretended to be the sweetest singer on the planet, but Madonna has a real mean streak: She showed that off at an Oscars after party in 2013. "She was rude to most people; she really behaved like a b***h that night," a guest says. On a recent international flight, Madge ignored her children, making them fly in coach while she enjoyed first class until they exited the plane and saw photographers. That prompted her eldest, Lourdes, to ask, "Mom, why do you only hold our hands when there are cameras?'
7. Cameron Diaz: She may always be smiling, but the 'Sex tape' star is not so friendly to her fans. "Cameron berated a fan after being asked for an autograph," a source tells Star. "Not only did she refuse to sign, but she lectured the fan about how dumb autographs are and completely humiliated someone who looked up to her!" In case you're wondering whether she was just having a bad day, in 2006 Cameron was named worst Hollywood signer by 'Autograph Collector Magazine.' Yes...that does exist!
6. Robin Thicke: Despite Robin's wife, Paula Patton, trying everything to keep her husband faithful, including inviting other woman into their bedroom, Robin has always had a wandering eye. But when "Blurred Lines" became a smash hit, he blatantly started chasing women and became a downright tyrant toward her. "Robin changed. He would talk down to Paula in front of others," says a source who believes that his latest attempts to win his ex back are all for show. "Robin doesn't deserve Paula after the way he treated her this past year and everything they've been through together."
5. Jay Z & Beyonce: All the single ladies would be put off by the real Beyonce. "She degrades people, especially women, on a daily basis," a source explains. "One time a young assistant spilled water on Beyonce, and she freaked out. She said the girl's makeup job was terrible and that her hair looked horrendous. It was so sad." At least it's easy to stay away from the couple. "Jay Z and Beyonce think they are so important and untouchable that they refuse to let any outside staff or security handle them when they are visiting a hotel or restaurant," a source adds. "If they enter an elevator, they must be sure it's cleared out before they enter." Well after that little episode with Solange, at least we get that behavior!
4. Kate Gosselin: The former poster woman for modern motherhood has revealed herself to be downright mean to...pretty much everyone. A former nanny went public, saying Kate was extremely condescending and had ironclad demands, including: handwash all knives, no grocery bags on the kitchen table; and walk lightly, or else she'll freak out! Her ex-husband, Jon, the subject of much of Kate's ire, says now that he's free, she's taking the anger out on their kids. "Kate treats people like garbage," Jon says. "She treats her kids like garbage."
3. Kim Kardashian: For the reality star, brotherly love only goes as far as how good your brother looks. Soon after Kim's bro, Rob, showed up in Paris for her nuptials, she sent him packing. "Kim was annoyed that he didn't slim down for her wedding and advised him it would be best if he just went home," a source spills. "Rob was disgusted by Kim's behavior and emphasis on wealth. After the way she treated him, he wanted nothing to do with her third wedding ceremony."
2. Meryl Streep: The multiple Oscar winner is the most talented actress of her generation, and she knows it. "Meryl is very cutthroat and blatantly mean," a source tells Star. "She's rude and snarky on set, especially to up-and-coming people who have always idolized her. She will roll her eyes at them, or point out mistakes to intentionally embarrass them." Meryl's reign of rudeness extends to her hometown, as well. "Meryl always makes rude remarks to her neighbors," the source says. "When she goes to the local grocery store, she will cut in front of people in line and cut people off with her cart." Mamma mia!
1. Ellen DeGeneres: The daytime darling takes the cake for being the Queen of Mean! "Ellen is a tyrant behind the scenes of her talk show," a source reveals. "If she isn't comfortable, no one can be. Ellen's tea water must be a certain temperature. If the studio is too hot or too cold, she throws a fit. She also demands that everything be spotless -- if she sees clutter, she instantly gets fired up." As you can imagine, with such a tyrannical atmosphere, staffers are fearful on set. "Everyone walks on eggshells," the source adds. "She seems like she would be fun to work for, but it's a dreadful experience."