The mixture of 2D animation and 3D animation are obviously mentor of comic books.
The source material that fireman comes from.
The idea that it isn't just CG animation but they were actually hand drawing on top of the CG is a brand new idea.
Using illustration and hand drawn imagery, From the old days of animation was something we wanted to infuse our movie with.
Because that's how comic books are made.
And to incorporate that all together in animations but comic book melted together form.
It was a new challenge for us.