'X Factor' Celeb Mentors: How Did Rihanna, Pharrell Fare?

It's clear "X Factor" isn't scared to tack on some star power to their much-hyped talent competition; just take a look at the judging panel. And after catching Thursday's night's delayed episode, which featured Rihanna, Pharrell, Enrique Iglesias and Mariah Carey (sort of), it's even clearer.

In an episode that sent all 32 contestants around the world to their assigned judges' homes, Simon Cowell (mentoring under-30s girl acts), L.A. Reid (mentoring under-30s boy acts), Paula Abdul (mentoring group acts) and Nicole Scherzinger (mentoring over-30s acts) took the wannabes under their wings, calling on their very famous friends to help out.

We here at the MTV Newsroom thought we'd take a closer look at the celeb mentors and their words of wisdom. Here's how they fared:

RihannaPartnering with L.A. Reid, the record bigwig who discovered her, Rihanna was open to voicing her opinions on contestants' vocal talents, confidence and commercial relatability. Right off the bat, the pop titan compared young rapper Brian Bradley (also known as the Astronomical Kid) to the likes of current industry MCs like J. Cole. Score: 8/10

Pharrell WilliamsPharrell is a versatile music pioneer. As a member of N.E.R.D., the hip-hop vet took time to point out the stronger members of Paula Abdul's group acts, stressing the technical skills of certain vocal talents. He also had no fear in offering up harsher criticism than the other mentors. "I would say they're good, but you know it. There are people who are coming in here with their harmonies as a prerequisite," he said of the Brewer Boys. Score: 8/10

Enrique IglesiasBeing a 36-year-old entertainer himself, Enrique may know what it's like to feel the industry's pressure on image, but the Latin pop star didn't offer too much of a critique for N! icole Sc herzinger's team of contestants. Iglesias did offer some constructive words at times, particularly for contestant Stacey Francis when he questioned her marketability. Instead, it was the former Pussycat Dolls frontwoman who had the most feedback. Score: 4/10

Mariah CareyMiss Mimi is undoubtedly the biggest star of the four-pack, but was she too big to appear on "X Factor"? Of course not. Yet, Hurricane Irene prohibited the pop icon from flying over to Simon Cowell's home across the pond in France. Vocal coach Savan Kotecha and producers Graham Stack and Ray Hedges were on site to help the judge narrow down his final team of contestants. We're hopeful that the songstress will make an appearance during the series, and if she does, Mariah, we have our eye on you! Score: N/A

What did you think of the celebrity mentors on "X Factor"?