For The Mask Vs. Deadpool we wanted to make the final part of the fight SUPER dramatic with three different kinds of lighting. Lightning strikes, gunshots, and a nuke blast all timed to music. SO, when making the backgrounds for it I made an ON and OFF version of each of the backgrounds to let animators do things Like control lighting/intensity, and move things like clouds out of the way for the super wide shot of the explosion. You can watch the last part of The Mask Vs. Deadpool fight here: