__________  is a cel animation that involves creating a series of 2D drawings by hand.

The term you're looking for is "Traditional Animation." Traditional animation, also known as cel animation, involves the process of creating a series of 2D drawings by hand, with each drawing differing slightly from the previous one. This technique allows animators to create the illusion of movement when the drawings are played in sequence at a speed of around 24 frames per second. Each drawing is often made on transparent sheets called 'cels,' which are layered over a background painting to create the final animation scene. Traditional animation has been a foundational technique in the animation industry, used in many classic animated films before the advent of computer-generated animation.