The effects in this piece was probably the most fun I've ever had editing video. The fire balls were recorded well after the studio shot where the actors were shot. The fire ball were just a lamp wick ball soaked in kerosene on the end of a wire. They were shot against a completely black background. Then I use a luma key to remove the black. This created a fire ball that I could put over any piece of video and it looked like the fire ball was there. Then using key frames I was able to animate the fire balls and give them character and life, and even allowed them to interact with the characters.
I had a BLAST with this piece. It just reminds me how much I love animation.