The idea is that some unlikely person is trained in three weeks to become someone different and then they have to pose in front of experts to see if their lack of skills can be detected in comparison to some other people who actually are who they are. The first one I saw part of was a young girl who looked nothing like a cheerleader being turned into one for some important football game. It was kind of fun seeing her get into the schtick and doing pretty well at it (if you can call smiling falsely, and jumping up and down with pom-poms anything being done well). I don't know if she really succeeded since I only watched her a bit. The second one I watched was Bill, the captain of the US Beer Drinking Team (I didn't know there was such a thing), being transformed into a sommelier. This turned out to be more interesting than the baseball game so I watched most of it.
Bill had as his training team a sommellier, a pronunciation trainer, and an appearance trainer. It was tough work for them. He knew nothing at all about wine - couldn't even tell red from white - he was a beer drinking football guy. He struggled with everything, considered quitting several times, and made a fool of himself during the practice sessions as he made mistake after mistake. They cut off his beard, trimmed his hair, dressed him well, taught him to speak "properly", changed him from Bill to William, etc. It was the fact that he bonded with the trainers that made him not give up and see it through; he was tempted to quit several times since he wasn't being successful and wasn't even having much fun.
During the real test in a fancy San Francisco restaurant, he and three other real sommeliers each served one of the four courses to three tables of judges. His coaches were watching him and commenting on his successes and failures. One customer asked him if some other wine might be better - his wine coach said "wow, he knew nothing about that wine and still gave an excellent answer". At another point, the appearance coach groaned "oh, he took the cap off his pen with his mouth - I hope nobody saw saw that".
Amazingly enough, one of the tables picked someone else as the fake - and it was considered a great victory since that table had a sommellier as the chief judge.