Last May, on a whim, I answered a casting call for Me, Myself and Irene, the latest Farrelly brothers project, starring Jim Carrey and Renée Zellweger. Snapshot of myself in hand, I drove to the designated hotel.

When I arrived, a line of several hundred people wound along the sidewalk. Somehow, naively, I had not expected such a crowd, nor had it occurred to me that anyone, particularly in northern Vermont, would come for any reason other than simple curiosity.

But there they were: well-dressed, freshly coifed children standing alongside Parents of Suburbia, photo portfolios in hand; Harley riders, arms folded, head shots tucked under their biceps; waify actresses in half-shirts that exposed bellybutton rings with casual purposefulness, sitting on the curb sipping bottled water and chittering about commercials in which they'd starred. And there were the Carrey wannabes, boring and embarrassing those around them with appalling impersonations of Carrey, as if the Fire Marshall Bill shtick were their own or they shared a unique bond with Carrey because they knew every line of his movies or, worse, they hoped to be discovered themselves by an incognito talent scout.

After an hour of waiting, a casting director appeared. Everyone perked up, preened and accorded erect postures as he doled out a sheet. When he left, the crowd buzzed with speculation. Did the casting director know Jim? Did he discover stars? Would there be speaking lines? How many roles were available? What were the odds of landing one?

Suddenly I realized that coming to the casting call wasn't enough. I wanted a part. And all the freaks around me were my undeserving competition.

I looked down at the sheet. It addressed on-set behavior:

Inside the hotel conference room, I sat with ten others at one of a dozen tables. Apprehension and anticipation lurked. I filled out the provided application; I gave my physical attributes and clothes sizes. Under the Special Abilities section I wrote "moonshining." An actor needs a gimmick."

I was lined up against a grey curtain, shot with a Polaroid, handed my photo and told to wait with the others in a row of chairs. Something was going on behind a curtain. Were we going to have to read lines, unrehearsed? Would it be decided right there, behind the curtain, if I had the goods? What if I was off and lost the opportunity to convey my true potential? What was happening to me?

My turn came. Behind the curtain, a friendly, professional woman stapled my questionnaire to my photos and said thanks. And then I was guided out into the daylight.

I went home and waited.

Two weeks later, at 11 p.m., I received a call. "We need you. Tomorrow. Bring a dark sports jacket and light blue shirt, the camera doesn't like white. And a tie. You're a federal agent." Would Jim be there, I wanted to ask. Would I get a make-out scene with Renée, get to put my semen in her hair, something raunchy and Farrelleyesque?

I went to Ames department store and bought a light blue button-up shirt.

Next day, on set, I was escorted by the casting director, Kevin, past the wardrobe and make-up trailers, beyond the catering trucks and sound and lighting equipment, to the basement of a church, to join two fellow Feds, Kyle and Bruce.

Kyle, like me, had no acting experience. But Bruce. Bruce was an actor. He was tall, dark and handsome, chiseled and weathered, with a wry smile. He had slightly vampiric teeth, and his network-anchorman hair greying at the temples suggested, the casting director in me thought, "Fed-gone-bad."

Bruce's eyes gleamed. He leaned back in his folding metal chair and said, "You never know what they'll use you for. They could tell us we're no longer Feds, tell us we're angels and give us wings. You have to roll with it. We may be given lines. But don't sweat it; if you can take directions, you can act. It's the look they're after."

Bruce had varying versions of the same story: "You know so and so," and he'd name an actor I'd never heard of. "He played the lead role in Eddie and the Cruisers?" or "He was Manson in Helter Skelter," or "He's Pattie Duke Austin's stepson. I worked with him," and he'd name a movie with a name like Assassin's Kiss. "Well," he'd say. "He's just a regular guy."

We got called to wardrobe. I looked for Jim and Renée. We all did. Inevitably, almost helplessly, we talked about Jim. That's what we called him: Jim. It was a way to save saying his entire name every time. It was a way to make him familiar, even though he wouldn't speak to us.

Onlookers, college kids on their nearby apartment porches and rooftops, watched us with binoculars.

In wardrobe, several women full of breeze and expediency fell on us and fitted us with new sports jackets and shirts. Flicking lint from our shoulders, they turned us around to get a good look at us. "Feds," they said. "Go to make-up."

In make-up they cut Bruce's and Kyle's hair. They dyed Bruce's greying temples. My cut, a summer buzz, was already federal enough.

Outside, we waited. We did not talk of Jim or Renée while among the crew. We were part of this. We felt very cool.

Kevin sidled up. "Today should go smoothly," he said. "No Jim. No Renée. No problems."

"Oh," we said.

"You guys might as well wait in the church."

Back in the church basement, I realized how removed we were from the action.

We waited three hours.

"This is how it goes," Bruce said.

Kevin rolled in at noon. "That's it. They're done. They cut the Feds out of your scene. You can sign out."

That was it. No Jim. No Renée. No part. Go home.

Next week a woman called at 10 p.m.: "We need you, and your truck, tomorrow. Bring two changes of clothes. Summery stuff. No black. No white." In a secretive tone she revealed the name of the motel where the shoot would be.

There were twenty extras that day, full of the good-natured bantering that takes place when strangers acquaint themselves under fortuitous circumstances: we were all chosen from the droves for a specific quality that was not outwardly identifiable.

We waited, for hours, outside, behind a rectory. It was hot; in the 90s. We lunched, Hollywood style. Pan-seared scallops with caviar. Duck á l'orange. King crab legs and beef medallions. Banana torte. Chocolate mousse. Opera bars. Crescents. Fresh breads. Salads and ice cream and pie.

I was sitting near the catering truck, catching my breath after lunch, when Renée appeared, affecting a strong Texas drawl and requesting king crab legs. She seemed a foundling. So slight. Maybe 5'2'' and 105 pounds. A body like an adolescent boy's, but a darling, womanly face. She was barefoot and tripped in the grass. A starlet. Not really a fan of hers, I still found it odd that I was not allowed to say hello. She looked sort of lonely. She might have liked someone to say hello. She tripped away to her trailer.

Later, I drove my truck onto the set. And there he was: Jim. He sat in a chair at the base of a lighting crane, sporting a crew cut and tight faded jeans and a shirt printed with cowboys. He was rubbing his palms on his knees with a nervous energy.

He was waiting.

I was told to leave. They needed my truck. Not me.

After sitting around for six more hours, reading and napping, I was finally released at 1 a.m., not a second of screen time.

Then came my break.

I was told to be at a train station at 6:30 a.m.

Bruce was there. He was wearing a sports coat and a Hawaiian T-shirt. I told him he was one dapper son of a bitch.

At eight a.m., thirty of us were taken to the set. I was seated at an outdoor cafe and given an empty Coke can. Bruce was paired up with a woman who was now his wife. Others were given porters' uniforms, or lemonade and pretzel stands, with attendant aprons and visors.

We were suddenly passersby, commuters and vendors.

The train would pull in. Jim, whose character was a Rhode Island state trooper with a split personality and an obsession with Renée's character, would throw himself from the train and beat himself up. When this commotion began, we were to gather around him.

Action was called. The train rolled in. I drank from my empty Coke can. The lemonade guy poured lemonade. Bruce and his new bride stepped off the train. We all pantomimed, moved our mouths in conversation without speaking, as directed.

Then, two cars down, Jim threw himself from the train onto an air mattress. He was shouting and cursing, his face contorted. I edged over to the commotion as he flailed and spit, then grabbed himself by an ear and dragged himself toward the station.

Cut.

The train backed up. We took our marks. Action was called. We did it again. A woman shielded Jim with an umbrella. Another misted his forehead. Another wiped the mist. We shot the scene again. And again. Ten more times. Morning became noon. But no one tired. Instead, the extras, feeling integral yet utterly replaceable, did their best.

It was then that I learned that Jim Carrey is a serious actor.

That is, even when shooting this ridiculous scene, he hit his mark. When he missed it, he grew frustrated: "Sorry," he said to cast and crew, as if apologizing for his $20 million price tag. "I can do better." Even when the Farrellys were pleased, Jim offered to do it again, improvising, feeling his way through, his energy level clearly rising, his eyes growing alert with the brightness of someone who has worked to get to the place where suddenly the ideas are flowing and who wants to stay there. His own twists were often funnier than the script, and the people around him seemed no longer cast and crew, but a live audience to play to. When he dreamed up a subtle, but significant slant, they could not keep from laughing and applauding when cut was called. I was on set with an actor who made a role, a movie, his own, one of the most highly paid people in his field, and someone who, when he worked himself up to it, was as funny and natural and ingenious as they come. Jim Carrey.

Lunch was called, and the affable and lunatic actor, who moments ago had seemed engaged with those around him in a necessary reciprocity to reach the place he needed to reach, followed his bodyguard swiftly to a waiting Cadillac SUV, replete with blackened windows, and was driven away to his rented penthouse condo, across the street.

I remembered being unable to say hi to Renée, and again thought it peculiar, this deliberate isolation. To be hounded by obsessive fans must be hell, but why not eat lunch with fellow professionals? Why remove oneself? Do stars, in some perverse, self-fulfilling prophecy, do exactly what's expected of them to add to the mystique of stardom, I wondered. In a way, is it part of a star's job? Would they be lesser stars if they were too approachable? I thought of Michael Jackson, Madonna, Michael Jordan, celebrities beyond their talent, something other than themselves, to the public, at least. Their names are brand names, trademarks that possess more weight and meaning than simple identification. But isn't that what celebrity is all about, what we all wish we could do: be doted on when we desire and then remove ourselves from people and places when we wish?

Then again, maybe Jim was just back at his condo practicing his lines.

After lunch, we shot a scene in which Carrey's character jerks off on a bench full of elderly women, asking, "Wanna see my weasel?"

The women, all extras, were supposed to run away, but they could only laugh. Jim told them, "Look, you're scared, I'm a crazy man, whipping his thing out, and if you don't get up and run, I'm going to get it all over you." He liked to affect seriousness, while inciting laughter. He suggested it might be funnier if all the ladies ran away, except one, who seemed to like what she was seeing. They tried this version, but unable to nail it in several takes, reverted to the script.

The women were still not acting shocked enough for the Farrellys, who, throughout my days on the set, were never anything but patient, professional and pointed with the extras, allowing the process to be enjoyable, but efficient. Jim told the women, "Imagine it has two heads." This tactic didn't work. They did take after take. Jim chased the women off the bench, pretending to jerk off on each one of them. He would pace by me after every take, always whispering to himself, "I got it all over them that time" or, "This is sick," as if it just dawned on him.

When frustration set in, Jim conferred with the Farrellys and crew members off set.

The next take, when Jim unzipped and whipped it out, he pulled out a huge rubber dildo the prop man had given him and waved it in their faces as he slobbered and howled.

Cut. Print.

Jim threw the prop high into the air and shouted, "First one to touch it is gettin' married!!"

I was on set four more days, playing in shoot-out and getaway scenes. I wore different clothes, but looked essentially the same. If a viewer knew what to look for, they would see that the gawker was later the lemonade stand guy or the man at a phone booth. But no one ever pays attention to background scenes. No one notices our nuance, our acting, except other extras. I can't watch a movie now without noticing the background, knowing the extras are pantomiming and not really saying anything, looking for them to appear elsewhere. It's a curse.

Those last days, I fell into a routine. Sometimes, when not in a scene, I no longer watched as Jim performed or Renée tried to get him to act like a person with one personality. I was getting used to the lights and cameras. I saw the directors and stars out in restaurants and bars at night. On weekends, I glimpsed Renée on the waterfront and at the farmers' market—no bodyguards, no boyfriend, just ambling along in a bandanna and sunglasses, sans make-up, contentedly walking her dog and shopping. I could have gone up to her and said hello. I could have explained that I was an extra in her film. I could have pretended that I didn't know who she was and walked right by her without looking at her. I could have struck up a conversation. But of course I didn't. She was a star.