Who's going to guest judge X-Factor tonight ?

For those of you who are unfamiliar as to how X Factor works, now that the 32 final contestants have been chosen, its time for the acts to sing at the judges' homes. Boys, girls, groups and oldies will divvy up and perform for their respective judges as well as some surprise heavy hitting guest stars!
We've already heard that Rihanna and Mariah Carey will be a part of this next round of judging, but now there is some man candy in the mix! both Pharrell Williams and Enrique Inglesias will lend a hand - and a voice - to the contestants tongith before they face their next elimination. One source who was on the scene of the rehearsals reveals:
"The acts were totally blown away meeting their mentors at these amazing homes – then it was even more nerve-racking performing for a guest judge. Some of the girls especially were delighted when they saw Enrique and Pharrell. The acts who met Rihanna were totally speechless – who knows how they managed to sing!"
We know we would have major difficulty! Such a group of talent - we'd have trouble just breathing!!!
Hopefully, these big names stars will bring in the big time ratings Simon Cowell has been waiting for!