by Steve Ryfle Dr. Phil just wanted to use the bathroom. A private bathroom, that is. And that's when the trouble started.

There wasn't a private bathroom, you see, and when Dr. Phil learned he'd have to relieve his celebrity self with the unwashed masses, he threw a hissy fit.

The story, which made the gossip columns in September, propelled America's favorite bald shrink--a guy who makes his living telling people to be nice to one another--into the ranks of prima donnas who pout, throw tantrums (a la Naomi Campbell) or telephones (a la Russell Crowe) when they don't get special treatment.

It also brings to mind that timeless question: Why do some celebrities let the fame, and all its related perks and privileges, go to their heads, while others don't?

"It depends on how much their stardom is part of their identity," says Yvonne Thomas, PhD, a Los Angeles psychologist whose clientele includes numerous Hollywood types, who will remain anonymous.

Thomas explains, "If (stardom) has taken over the majority of their identity, then they start to buy into, 'I'm better than other people, more privileged, more special than other people. And therefore I deserve to have more than other people, and I deserve to have things when I want it, how I want it. I deserve the most expensive stuff, I deserve special treatment.'"

If absolute power corrupts, so does absolute fame. Who can blame stars for losing perspective when they're suddenly blessed with fame, power, money, sex, lots of free stuff, and a free passport to the front of the line.

It can happen even to those who might seem incorruptible. When Oprah showed up at a posh Paris boutique 15 minutes after closing time, and wasn't allowed to shop, she went public with her gripe. She insisted she was denied entrance not because the store closed 15 minutes ago, but because she was considered "not chic enough or the right class or the right color or whatever" by the store staff. Oprah pressed the issue until the store's brass publicly apologized, all the while insisting she wasn't "playing the celebrity card."

Last year, Hugh Grant was supposedly heard shouting "Don't you know who I am?" when he arrived at a UK restaurant with friends, but with no reservation, and was told there were no tables available. Clint Eastwood once punched a hole in a hotel room wall because he was ticked that the closet door wouldn't open. Melanie Griffith--not that she ever seemed incorruptible, mind you--supposedly threw a tantrum she tried to buy a pink iPod mini and was told there weren't any in stock.

And then there are the dozens of rock icons who've thrown snit-fits when their backstage riders--contract clauses detailing all the food, drink and other accouterment that must be provided in the dressing room--were not followed to the letter. The most ridiculous was probably Van Halen's "brown M&M clause," which banned brown M&Ms from the band's candy dish. Back in the 70s, David Lee Roth once discovered a few of the offending chocolates and freaked out, doing $85,000 worth of damage to a backstage room.

But there are those who don't let fame and power change them--at least not completely. Thomas points to the Tom Hankses, the Ron Howards, the Al Pacinos and the Meryl Streeps--stars who have thus far avoided throwing public tantrums while maintaining low-key public images.

How celebrities behave, Thomas says, pretty much boils down to how they were raised.

"If they came from a stable, grounded family, and they currently have a good support system of family and friends, these are the people who are able to maintain that humbleness, and that sense of the real them, the genuine them."

The Dr. Phil incident reportedly happened at a charity event hosted by California's first lady, Maria Shriver. Dr. Phil was the keynote speaker, but he became irritated upon arrival at the event, and learning that he wasn't going to be introduced by Gov. Arnold Schwarzenegger, due to a schedule conflict. "I am not happy," the TV shrink reportedly said. With that, and the bathroom flap, Dr. Phil refused to give his speech, until Shriver shamed him: "My 7-year-old doesn't act the way you do."

Thomas won't speculate on what makes Dr. Phil or Melanie Griffith or David Lee Roth act the way they do, but she said celebrities often make inhuman demands and expect adulation and special treatment because they were emotionally deprived as kids, and now they're trying "to fill up a void of something they didn't get emotionally when they were growing up.

"Bottom line, if a person predominantly defines themselves by this celebrity identity and they've forgotten who they were before, that's completely about insecurity. ... It's definitely a compensatory mechanism, as we say in therapy terms."