An opinion about utilidors, etc.
Ok, here's a few facts about utilidors. If I can just qualify myself; I used them for several years.
First, please don't go into areas marked "Cast Members Only". Safety (insurance and legal), show and security issues all apply and are real. In recent years, they put cameras throughout the utilidors so it really is not a good idea to go explore them. If you are curious, then head over to Guest Relations and sign up for a tour, please. You can do that and will learn more and enjoy it more, with a cordial guide.
I do understand the curiosity as it was a big part of the reason I came to work at WDW to begin with. Reality is, though, it is pretty much the same as any hotel basement or other commercial unthemed space you might wander into at a mall or wherever. Not magical! About as interesting as the manager's office at Wal-Mart or the utility sinks at McDonald's.
A major reason that Magic Kingdom has their utilidors is the Florida land was swampy and they built the themed areas of the park on what is actually a "second floor". The utilidors are a ground floor. And yes, people in costume can get around to their various spaces from wardrobe fairly efficiently.
At Epcot, there are a few utilidors for getting around the central part of future world, but world showcase has bus service all around the back perimeter. No need for a basement!
Same thing with the Studios and DAK. Bus service (and bicycles to borrow) out at the perimeter gets everyone where they need to be, in costume and without walking through areas "out of theme".
Again, please, if you're curious, try the tour. See guest relations about it. They get great reviews from people who have gone on them.
Since I left Disney's employ, I don't go back there. I enjoy the parks as a guest and really, really think that's the way to see the parks and resorts.