I made a square in Gimp and used Gimp's projective function to distort it:
Then I transformed it back to a square =D :
And here's a table with square checkered tablecloth:
And abra kadabra, it's square!
Ok, so that was a little boring. Let's get to the real stuff. For my Bells and Whistles, I used a laplacian pyramid to improve blending. Thankfully only 2 levels were needed to get a good outcome.
Before:
After:
P.S. Did you notice the people on the right? No?! Look harder!
Before:
After:
Happily Ever After:
Before:
After:
All base files can be found here. And all results can be found here.