Ok, the keys do fit. You will have weird spacing between the keys, much like the MacBook, but that is not the issue.
Here is the issue. They fit, but they are sideways. The scissor mechanism on the MacBook pro is vertical, whereas on the MacBook they are horizontal.
Now, it is possible that the MacBook Air keys, or the wired USB keyboard keys are vertical scissors, so they would work. And, the MBA's keys are backlit, so you would still have that too.