Any popstar worth their salt knows that to survive in the business, you have to reinvent yourself every so often - and the King of Pop must know that better than any.

But quite what Michael Jackson thinks this look will do for his career is anyone's guess.

As he approaches his 50th birthday next month, the singer's appearance just seems to be getting more and more bizarre.

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Looking every inch the invalid, Michael Jackson is wheeled around Las Vegas

Pictured on a visit to a toy and book shop near his current home in Las Vegas, the singer was slumped in a wheelchair wearing pyjamas, a dreadlocked wig, a surgeon's mask, a baseball cap and sunglasses.

Such theatre was presumably designed to prevent shoppers from discovering his true identity.

The irony is of course that Jackson is now better known for wearing such ludicrous disguises than not.

Indeed he would have stood a much better chance of not being noticed had he strode into the shop without any disguise - and had not pulled up in four cars filled with his eight-strong security team.

It remained unclear last night whether Jackson, who is most famous for his footwork and in particular his moonwalk, actually needs the wheelchair to get around or whether he was just using it as a prop.

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He has been spotted both with and without the chair in recent weeks.

He has battled numerous health problems over the years, having being diagnosed with lupus and vitiligo and the amount of surgery he has had has rendered him unrecognisable from his former self.

Following accusations of child molestation in 1993, Jackson lost a massive amount of weight.

In late 1995, he was rushed to hospital after collapsing during rehearsals for a televised performance; the incident was caused by a stress-related panic attack.

During his further trial on molestation charges, the singer again suffered from stress-related illnesses and severe weight loss.

He has also been addicted to various painkillers over the years to cope with the accusations levelled at him.

The last time he was in the chair was to watch the Ultimate Fighting Championship in Las Vegas in May at the MGM Grand hotel.

On that occasion, he also draped a coat around his face to try to disguise himself. But as always, the peculiar appearance only drew more attention to himself.

On this occasion, Jackson arrived with his three children, who were unusually unmasked, and headed straight for the children's book section, where he remained alone for some time.

An eyewitness said: 'They arrived at the Barnes and Nobel shop in Las Vegas on Monday afternoon.

'First Michael was in the childrens' section on his own in the wheelchair reading books. The three children were at another table with the bodyguards.

'He was in the children's section for about half an hour. He then went to the music section and was sitting in the chair looking through various books.

'But this time the children were in the children's section. Then he pushed himself around in the wheelchair for a while and ended up in the magazine section.

'He was in the shop for about two hours in total. There was no special treatment. The shop was not closed to the public at any point.

'There were quite a few members of the public in the shop who knew he was there but no one approached him.

'To be honest, he looked a bit weird wheeling himself around covered up in a surgeon's mask and that is probably what freaked people out to not want to approach him.

'When they left the shop, the children came out first and he was wheeled out behind them. He never left the wheelchair at any point in the shop.'

A Jackson family friend indicated last night that the wheelchair was indeed needed for a recurring back problem that Jackson has had ever since his performing days.

'He has a problem with his back which surfaces from time to time,' the friend said.

Jackson is currently living in Las Vegas trying to land a residency at one of the big venues in the city to clear massive debts he has accrued.

His career fell apart and he spiralled into debt - despite selling 170million records worldwide - after a string of child sex allegations were made against him in 2005, of which he was later cleared.