I had a very active imagination as a child. Combine that with the fact that I had no siblings and lived in a neighborhood with no other children who liked to play, and I had to entertain myself most of the time. I got very good at it.
Forward thirty years, and I now have two children of my own. With two children, pretend play is still a hit, but it gets even more inventive! Wow, the fun I missed out on without a little brother.
We're currently reading The Trumpet of the Swan by E. B. White. My daughter ran around all morning, pretending she was Lewis. That meant I didn't hear her voice at all. Anytime I'd ask them a question, she'd get in front of me, huge smile on her face, and nod vigorously and flap her "wings." My three-year-old son was the cob (the father swan) and he ran around flapping his wings, ko-hoh-ing and talking a lot. The area rug in our living room is now a pond, and I'm the mommy swan.
Perhaps the strangest thing I've ever seen them pretend happened after they watched an episode of the BBC documentary Planet Earth. My daughter decided the next morning that she wanted to be the baby caribou that got caught and eaten by the wolf. Little brother, naturally, was the wolf.
I figured that was normal, but she went back to her Baby Caribou act this morning (a month later) before she broke out in her Mute Swan demo. Between those bits, she said she was the fish that hides her babies in her mouth (cichlids).
This is pretty typical of kids, I know. But it tells me they're paying attention when I'm reading those chapters at bedtime or when they're watching educational stuff. Just as much so as when they're watching "Little Einsteins" or "Max and Ruby." And I believe, from my own limited observations, that pretend play helps cement the things they've learned.