Holy cow, I wrote a book!
Some people from my knitting group have been among those assisting in the preparation of today's episode of the knitting show Knitty Gritty on The Do It Yourself Network.
Stop reading if you don't want the television illusion shattered, or at least cracked a bit.
Each volunteer was assigned a section of a sweater to knit. The show's host will take those pieces and do some short demonstration with it, perhaps sewing pieces together or illustrating one of the trickier parts.
After each volunteer made their assigned part, they also had to start working on the same sweater again, but not to finish it. They will be in the background knitting while the host does the feature demonstration.
What's more, each volunteer has already been told what problem they will be having with the sweater, so that the host can help extricate them from whatever mess they got themselves into. Nevermind that they already made the sweater that the host was using in the demonstration just a few minutes ago. Clearly, they know what they're doing; they did all the knitting!
If you thought the hosts of these shows actually did the cooking/sewing/knitting/whatever, well now you know better.