Dozens of showbiz celebrities flocked to the television presenter's wealthy pad in Hampstead, north London to find it almost unrecognisable as the front of the building mutated into a spooky cartoon house of horrors!
Every year Ross opens his home to local children as a special Halloween treat while famous celebs, adorned in seasonal fancy dress, gather in large numbers for one of the showbusiness events of the year.
Among the VIPs attending were comedian and 'Britain's Got Talent' judge Michael McIntyre and fellow entertainer David Walliams of 'Little Britain' fame. McIntyre dressed as a dapper Dracula while Walliams showed up as an evil-looking mediaeval executioner complete with a black leather waistcoat, knee high boots, bobbed wig and imitation axe.
Funnymen Jimmy Carr and Daria O'Briain arrived with Carr carried into the building inside a cage held high by a King Kong character while O'Briain was dressed as a blood-covered mime artist.
Simon Pegg appeared as a fearsome looking biker skeleton resplendent in leather boots and fiendish make-up with TV comedian Frank Skinner appearing in a more subdued costume, dressed as a plain priest figure from the horror film 'The Exorcist.'
Broadcaster Louis Theroux attended the festivities dressed as a zombie prison inmate and other guests that turned up to the glittering party included Claudia Winkleman, David Mitchell, Dexter Fletcher, Heston Blumenthal, John Bishop, David Baddiel and Mark Gattiss from 'The League of Gentlemen.'
And Area 51 were on hand to make the party a true spook-tacular success with a large team of performers and six construction workers on site all day and night.
The company's oogie boogie man was one of the star attractions on show and proved popular with paparazzi press photographers who flocked to photo Ross standing next to the oversized ghoulish character.
Other Area 51 entertainers included ghostbusters, Frankenstein's monster, steampunks, a human statue and the Mr. Staypuft character while children and celebrities enjoyed being entertained and photographed with the company's oversized KISS rock band characters.
Hundreds of children turned up to marvel at the costumed characters and enjoy candyfloss and sweets donated free by Ross and his wife Jane Goldman.
The actual process of transforming the Ross residence into a haunted homestead was a frenetic and fast-paced mission for the six-strong team of Area 51 staff who carried out an operation lasting 24 hours from start to finish.
Initially, Jonathan Ross had to choose from a number of options on offer from Area 51 and once he chose the cartoon house of horrors, the Warwickshire-based firm's design team set about supplying a set of drawings and then the scenery was built in-house at the firm's extensive workshop.
A full-day build began before dawn with a weighted scaffolding structure on telescopic poles with scenery attached to it being sited directly in front of the building's facia.
The structure featured UV-reactive frames festooned with giant pumpkins and other Halloween-themed decor while 15 UV lights and a large CO2 jet system were also installed to add extra fun and pizzazz to the proceedings.
Speaking on his Twitter account, Ross, who is married to fellow TV star Jane Goldman, thanked Area 51 for helping make the annual bash a big success.
He wrote: 'Needless to say I didn't do the front of my house on my own...thanks to Rich and Area 51 for the inspiration and sweat!!'