According to The People, organisers spilt 24 bottles of Sapporo lager onto the X Factor judge's £400,000 Rolls Royce.
However, the night seemed to improve from there.
Guests at the bash included Cheryl and Ashley Cole, Dannii Minogue, Louis Walsh, David Hasselhoff, Kelly Brook, Katie Price, Mariah Carey and Gordon Ramsay.
Leona Lewis, Westlife and Il Divo were on hand to provide the entertainment, along with US group Earth, Wind & Fire.
A source told the newspaper: "Earth, Wind & Fire are Simon's favourites. It was hard work to get them there, but he managed to pull it off."
The celebrations continued well into the night, although all those under the age of 18 were asked to leave at 10.30pm.
"Simon wanted kids there because some of his friends have got them, but he was also aware that some of the fun wasn't suitable for them," the source stated.