Kristen Bell's Birthday Meltdown and Other Spastic Celebrity Moments

Actress Kristen Bell delighted fans everywhere when she gushed about her love of sloths during her Tuesday appearance on "Ellen."

It all started when her fiancé, "Parenthood" star Dax Shepard, told her he had a surprise for her on her 31st birthday. He told her to go back to the bedroom when a delivery arrived - and she just knew it was a sloth.

"I start to have a full-fledged panic attack," Bell told DeGeneres. "I don't know how to compete with all this emotion, so I just kind of crawl up on the bed and I'm crying so hard. Dax knocks on the door and he has a video camera and he's like, 'Surprise! I want you to come out into the ... are you all right?!' And he sees me basically fetal on the bed."

He did have a sloth - and she was more than delighted. The little animal - named Melon - hung out at her birthday party for a few hours. Of course, Bell thought Shepard was just the best person ever.

It. Was. Adorable.

Bell clearly takes the Academy Award for "Most Adorable Meltdown." However, not all celebrity meltdowns are so cute.

Tom Cruise

Who can forget when Tom Cruise appeared on Oprah in 2005? No one, that's who. The superstar actor was more than a little excited over his new relationship with Katie Holmes - and he just had to jump on a couch to celebrate.

"I just felt that way, and I feel that way about her," he told Oprah of his reaction. "I can't even articulate it, to be honest. That feeling, that connection. Just who she is and what she means to me."

The best product of their union? The super sassy diva known as Suri Cruise.

Tyra Banks

"America's Next Top Model" creator Tyra Banks likes to talk about herself - a lot. That's what made her meltdown during a season of "ANTM" all the more hilarious. The model, author and Harvard Business student gave an eliminated model, Tiffany, an earful during the cut for being disrespectful and acting like it was all a joke.

"I have never in my life yelled at a girl like this! When my mother yells like this it's because she loves me. I was rooting for you... How dare you?" she screamed at the young model.

Bill O'Reilly

Bill O'Reilly is now a host on Fox News, but once upon a time he hosted the tabloid show "Inside Edition." It wasn't easy for the anchor - his meltdown over a script was recorded and released for all the world to see.

"F**k it! We'll do it live!" he screamed at producers. We'd like to think that this was the only time his crew got to see his ugly side, but we're pretty sure it wasn't a one-time thing.

Which is your favorite celebrity meltdown?

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