The talk show host who asked me to put vodka in her water bottle... pop singer with an ego problem... and A-lister who's VERY cheap: ROB SHUTER has met every big star in Hollywood, now he's outing their secrets

Before becoming an entertainment columnist, I spent more than a decade working behind the Hollywood curtain, as publicist for some of the biggest names on the planet, including Jennifer Lopez, Jessica Simpson, Alicia Keys and even Diddy.

I sat in celebrity dressing rooms, rode in their cars and stood backstage watching how they behaved when they thought nobody important was looking. 

That was when I discovered who they really were, away from red carpets and flashing cameras.

Jenny from the Block

Jennifer Lopez was never just a celebrity. She always saw herself as a brand. For me, observing her was a masterclass in the practice of self-control.

Jennifer's every entrance was choreographed, every public smile calibrated and every detail – lighting, accessories, timing, even the door she walked through – mattered.

Was it exhausting? Sometimes. 

Impressive? Absolutely.

I witnessed Jennifer's exquisite discipline and poise up close when I accompanied her to the 2004 Golden Globes, just days after she and Ben Affleck announced the end of their engagement.

I had arranged for her, as a presenter, to enter and exit the Beverly Hilton Hotel through a side door, avoiding the three-ringed paparazzi circus that awaited her arrival.

But Jennifer refused. She had nothing to hide.

Other celebrities rolled their eyes and cracked jokes when she walked that red carpet with her head held high. Jennifer didn't care. She understood something they didn't: If she hid that would become the story.

Instead, she gave them something else to talk about. Jennifer Lopez taught me an enormous lesson about fame and life: If you don't define yourself, someone else will do it for you.

Smart blonde

Jessica Simpson was the opposite of Jennifer but equally impressive. I worked for her in 2005 and 2006.

Warm and hilarious, Jessica had the rare ability to make everyone around her comfortable. She made everything look effortless. But Jessica's ease belied a steely determination.

When her marriage to Nick Lachey ended without a prenup, she had to write her ex a very large check.

At the time, Jessica turned to me and said: 'I've made that much before. I can make it again.'

No self-pity. No victim routine.

Jessica was also incredibly generous. I never picked up the check at dinner or drinks with Jess. Though her sister Ashlee was a different story.

Once, when we stopped at Chipotle together, we paid separately. That still makes me laugh.

The ego

I never worked for John Mayer. I never even met him. But I was around Jessica when they began seeing each other on-and-off starting in 2005. That relationship broke her heart.

While they were dating, Mayer gave her DVDs of himself performing live.

Not flowers. Not chocolate.

John Mayer apparently thought the ultimate romantic gift was more John Mayer. It remains one of the most aggressively on-brand gifts I've ever heard of.

The relationship finally ended for good after Mayer gave a controversial interview to Playboy magazine in 2010 during which he referred to her as 'sexual napalm.'

He apparently meant that as a compliment, but to Jessica she could not abide a breach of trust.

Sad story

I never represented Wendy Williams, but I appeared on her talk show many times. She could be hilarious, generous and astonishingly quick. She could also be brutal.

Wendy had an uncanny ability to find the hidden rooms where people stashed their insecurities and if she thought there was a laugh behind those doors, she'd kick them open.

After her show ended, our relationship became very different, even as Wendy's health declined.

Once, she called asking me to bring bottled water to her apartment, but wanted me to empty the bottles and refill them with vodka. Another time, she pleaded with me to help her sell her designer bags because she needed cash.

I, of course, refused her requests. Wendy taught me that being someone's friend means being the person in their life who is willing to say no.

The Daily Mail contacted Wendy's representatives for comment.

The diva

Alicia Keys is offensively talented, polished to a shine and a bit of an elitist.

Ironically, for all her gifts, booking Alicia to major fashion covers was surprisingly difficult.

Vogue passed. Harper's Bazaar passed. I ultimately secured her first Elle cover in 2005 through a quid pro quo involving Jessica Simpson, someone Alicia didn't respect as an equal talent.

In the celebrity world, perception and reality rarely intersect.

Bad vibes

Sean 'Diddy' Combs was magnetic. That encouraged some, including myself, to look the other way.

I never witnessed anything illegal, but I'm troubled by the warning signs I dismissed.

A metal detector at his home. Armed men around his cars. Everything felt like a display of importance. Now, I recognize these things as methods of control. But while I worked for Diddy, something else jumped out to me: He could be shockingly cheap.

During a People magazine Most Beautiful photoshoot, I watched him empty the minibar in a hotel suite, leaving the magazine to cover the charges. He seemed determined to never pay for something that someone else would cover.

At the time, I dismissed the behavior as an eccentricity of extreme fame. Today, my takeaway is about myself: proximity to power can make you blind to behaviors that would raise alarm bells.

My friend

Ali Wentworth is simply the best. Funny, naughty and effortlessly cool, Ali didn't require the machinery of celebrity to make herself interesting.

We traveled together while I handled publicity for her morning show, Living It Up! With Ali & Jack. I once got off a train crying because she had made me laugh so hard.

Her stories about her mother, Muffie Cabot, who had served as Nancy Reagan's White House social secretary, were hysterical. Somehow, Ali could make even her mother's love of pea soup funny.

Of all the famous people I encountered, Ali was the person I wanted as my friend.

The legend

When I needed a celebrity to tape the pilot of my new VH1 TV show The Gossip Table, suddenly, every famous 'friend' who I'd helped in the past became unavailable.

Then I called Joan Rivers.

I explained what I needed. Her response was one word: 'When?'

No negotiation. No calculations.

After years being surrounded by fame, that's the lesson I cherish most: When somebody needs you, show up.