Sacha Baron Cohen's Bruno lands on top of a shocked Eminem

Sometimes an unexpected moment in the spotlight falls right into your lap.

Unfortunately for Eminem, it was 6ft tall, wearing fluffy white wings and displaying rather too much bare behind.

Even more unfortunately, the 36-year-old rapper had an immediate sense of humour failure.

In your face: Sacha Baron Cohen's Bruno lands on top of a shocked Eminem at the MTV Movie Awards in Los Angeles on Sunday night

Heavens above: The prankster as Bruno the Austrian fashion designer makes his extraordinary entrance

No doubt finding a scantily-clad Sacha Baron Cohen suspended from the ceiling in a harness and heading straight for your seat is alarming to say the least.

But as the actor landed on Eminem, only the audience at the U.S. awards show saw the funny side.

Screaming for Baron Cohen to get off him Eminem yelled: 'Are you serious? Are you f****** serious?'

Then with help from his bodyguards, he struggled free of his seat and stalked out of the stadium as the audience roared with laughter.

Debate is currently raging about whether Eminem was in on the joke or not. If he was, it was a virtuoso performance in appalled indignation.

Is it a bird, is it a plane? No it's Sacha Baron Cohen descending from the rafters at last night's MTV Movie Awards in Los Angeles

Puzzled: A bemused Eminem looks up and sees Baron Cohen coming towards him

Baron Cohen, whose characters include the outrageous Ali G and Borat, made his astonishing entrance at the MTV Movie Awards on Sunday night.

Wearing angel wings, knee-high white boots and a barely-there thong, he appeared as his Austrian fashion designer character Bruno to present the best male performance prize.

But instead of walking on to the stage at the Gibson Amphitheatre in Los Angeles, he was lowered in on wires.

As he descended, Baron Cohen, or rather Bruno, appeared to get into difficulties and started spinning upside down.

'My kugelsack! My kugelsack!' he wailed.

Caught in a trap: Eminem is trapped by the jockstrap-wearing Baron Cohen and needs the help of his burly minders to get free

Help me: The full horror unfolds

'The wire is trapped round. Help me! Let me down! One of the wires is trapped around my kugelsack.'

TV cameras cut to Eminem, who had performed at the awards show earlier in the evening, gazing up with concern from his seat.

Then, ominously, a single feather from Bruno's outfit floated down right in front of Eminem's face.

Seconds later, he was faced with something much, much worse.

Eminem, who regularly mocks celebrities in his rap songs, was disgusted as Baron Cohen flailed about on top of him.

As the singer's bodyguards finally managed to drag him off, the actor cracked a stream of jokes.

'Don't touch me guys, I already have a boyfriend,' he said. 'Let's continue this in my hotel room.'

As Eminem got up to leave, Cohen made a mocking reference to one of his songs and shouted: 'Is the real Slim Shady about to stand up?'

Eminem, who released Relapse - his first album in five years - last month, is not used to being on the receiving end of jokes.

View from above: The bizarre scene witnessed by the celebrity audience brought the house down

Joke's on you: Cameron Diaz was one of the celebrities caught on camera laughing or looking stunned

On his new album he teases ex-girlfriend Mariah Carey, jokes about sleeping with Sarah Palin and compares reality TV star Kim Kardashian to a drag artist.

Amy Winehouse, Elvis Presley and Lindsay Lohan are also targeted.

Eminem's spokesman refused to comment on the incident.

We are not amused: The rap star storms off as a laughing Baron Cohen is hoisted upwards

Exit: Eminem stormed out of the ceremony soon after

A spokesman from MTV's UK office said she had spoken to colleagues in the U.S who claimed they were given no prior warning of the prank. That would hardly be surprising.

Baron Cohen's characters all work best with unsuspecting victims.

Bruno, the star of his latest movie, tricks everyone from Paula Abdul to stuffy Republican senators into making fools of themselves.

The film - for which he has been paid £18million - has been billed as even more outrageous than his 2006 hit Borat, which featured a gauche reporter from Kazakhstan travelling to the U.S. and interviewing unsuspecting victims.

Similar controversy is sure to hit the Bruno film. In it Baron Cohen mocks his friend Madonna by having Bruno and his boyfriend, Diesel, adopt a baby from Africa called David. He apparently sent some flowers and a note to Madonna saying 'no hard feelings'.

Stunt man: Sacha Baron Cohen seen arriving at the MTV Movie Awards, the stunt will no doubt thrust him back into the spotlight ahead of the release of his new film Bruno

Bruno also forces himself on to the stage at Paris and Milan fashion weeks, getting a fashion designer to agree that the unfashionable should be sent to concentration camps to taught how to dress.

But the very fact that Bruno is due to be a hit means we will probably see even less of its creator.

After the success of the Borat movie, he withdrew to his £10million home in Hollywood, where he lives with girlfriend Isla Fisher and their two-year-old daughter.

After all, once his characters become too recognisable, the concept of tricking people into thinking they are real interviewers just doesn't work.