Not sure of a tutorial, but shoot in 2 locations, and match camera height & framing. Add some scaling/stretch type of effects, camera shake and then hide everything with a lens flare.
Johnny Cuevas, Editor
ThinkCK
“I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work.”
—THOMAS EDISON on inventing the light bulb.