Vector shapes in the paint editor, plus walk cycle animations.
These sprites are animated with a "walk cycle" script. Draw your sprite with the Vector tools so that shapes can be easily altered. As you draw, think about what parts of the sprite will change from costume to costume. Draw those parts as unified (or grouped) shapes so that they can be copied, pasted, and then changed. Your ability to play through the drawing while planning ahead for the animation will become one creative process as you work and explore. Think "flip book" and you'll understand the concept.