Walk-in reservations are much more common during a slower time of year. Here's an example: on our last day back in late April 2001 we checked out of Corando Springs and headed to the Magic Kingdom. Our original plan called for dinner at the Contemporary, and then drive back to Miami.
Fortunatvely it didn't work that way. After a few drinks at the Outer Rim Lounge, we decided, "We're tired. Let's see if anything's available." I marched down to the lobby with my best friend's girlfriend and asked the CM at Check-in (there was not a soul around). "Do you have any rooms for the night?" Sure enough there were! We ended up paying a Florida Resident rate, and split into five people it was a very good deal. We dined at the Concourse Steakhouse, had mor edirnks at the Outer Rim, and took a midnight swim at the pool. The next morning, after breakfast at Kona Cafe, we left fully refreshed at noon. Now THAT's a vacation.