The guest judge is Robin Gibb. A musical montage reminds us that Robin was always the Bee-Gee with the worst hair, which at certain points was quite the achievement.

The show gets underway with Josh "The Permanently Furloughed Marine" Gracin singing "Jive Talkin'." He starts off well but then, apparently craving combat, he stages a sneak attack on the audience and the camera. Pacing and trying to strut, he's soon out of breath and his hold on the tune suffers a bit. The crowd is still clearly enthusiastic. Randy says Josh did his thang. Paula says that Josh never "gyps" the audience, which will now provide a rare test for the Gypsy Anti-Defamation league. Simon calls the performance "manic" and says Josh shouted a bit, but declares it "not bad."

Clay Aiken chimes in next with "To Love Somebody." The song takes a really long time to kick into gear, which is the fault of the arrangement more than anything else. In a black suit and electric blue tie, Clay seems to be biding time until the chorus, where his voice comes through in fine form. He shows a nice and new richness, selling the emotion once the song becomes complicated. Randy, stuck in a verbal rut early on, says that Clay did his thang and says that he's obviously trying to win. Robin says that Clay sang it the way it's supposed to be sung. Simon says that of all the performances he's seen on "Pop Idol" and "American Idol," this was one of the best.

Kimberley Locke falls victim to an awful backing track on "I Just Wanna Be Your Everything." As is often the case with Kim, she starts off a bit tentative and gets engulfed in the first set of background vocals. She rarely stays lost for long and finishes well. Randy is either really enjoying the evening or else he's been replaced by a cyborg with a limited vocabulary. He issues his second straight version of "you're really trying to win this thing." He chooses not to point out that she did her thang. Paula calls her a classy gal. Simon says it didn't do it for him and that it was "sweet and ordinary." Paula seems chagrinned to be anywhere near Simon.

Ruben Studdard follows with "Nights on Broadway." After a couple so-so weeks and a voting scare last time out, Ruben lets loose a tiny bit. He?s never going to break into Hammer-esque dance moves, but he does something better. He has such control over the stage that all he needs to do is put his hand up and everybody in the crowd (and no doubt a few people in the home audience) snaps with him. The judges are happy to join the lovefest. The Randy-bot points out that Ruben did his thang. Paula says that Ruben rocks. Simon says that without Ruben the competition wouldn't be the same.

The night loops back with Josh singing "To Love Somebody." Don't the contestants know what's being sung each week? There's really nothing Josh can prove from singing the same song as Clay just minutes after the uber-gelfling. Josh's rendition, featuring a newly affected vibrato, is actually quite fine. He holds the melody well and his arrangement goes through the song's dull parts much faster than Clay's did. When he gets to the chorus, though, he lacks Clay's burst of vocal revelation. It's good, but a relative letdown. Randy-bot gives Josh his props and says it was the best he's ever heard him sing. Simon says it was risky, but Josh pulled it off.

Here's a simple question: If you're in the final four of a competition like this, do you waste a performance on such a trifle, showing that you can make light of your liabilities, or do you choose a more serious song that displays your strengths? Clay would have been better served with the latter. His version of "Grease" is good, but it's a baked potato and rubber chicken away from dinner theater and based on his macabre interpretation of hip thrusts, the poultry had better be juicy. Clay's lucky his first performance was so impressive.

The first three judges seem pleased, though. "I'm just sitting here laughing," Randy-bot says in a way that makes it sound like praise. Paula says Clay shook his thang, which seems odd. Clay has no "thang." Simon, also sitting there laughing, has only one word, "Horrible." The boos are deafening. Simon even draws a disapproving grimace and televised thumbs-down from a certain purple-haired Zap2it.com staffer sitting directly behind him.

Kimberley Locke again falls victim to the evil disembodied back-up singers, covering "Emotions." She picks up far quicker this time and shows off the most dynamic range of anybody remaining in the competition, adding some nice falsetto grace notes. The first three judges are all praise, but Simon is again on the fence, saying it wasn't her best night.

The show closes with Ruben whose "How Can You Mend a Broken Heart" is the performance of the night. This is a man whose voice you can just be happy listening to, whose voice you can imagine pouring from a radio. The best part of the song is watching Robin Gibb in the front row, eyes closed, mouthing the lyrics. Randy-bot calls Ruben "dawg" and says he did his thang. Robin calls it the best version he'd heard anybody do of their song. Paula says Ruben makes everybody feel warm and fuzzy. Simon says both songs were sensational. Ruben stumbled last week and probably made the bottom two as a result, but this week he stepped back up.

Josh ought to be a given for the bottom two this time around. This was perhaps his best week yet, but it's just his time (or past his time). Clay's super first effort will probably be enough to erase his Grease-y misstep, dropping Kimberley to the bottom two.

If anybody besides Josh is voted off this week, it will be an upset, but as they're fond of pointing out, on "American Idol," anything can happen.