I illustrated these beloved characters many years ago. Going through my old portfolio, I decided to scan and retouch them in Photoshop. My original was colored with marker and color pencil, and inked with Rapidograph on white Illustration board. 

Original before and Photoshop after. The big difference is the background which helps Donald's face & body pop, but I made subtle changes and improvements throughout, such as modifying all the original black strokes to complement their fills, see details below.

Years ago I originally drew this using marker and ink (see the comparison 2 frames below). It was flat, unappealing and remained more or less unfinished. Again, for practice I tried giving it new life in Photoshop.

In addition to colorizing the black strokes and adding shading to the fills, I applied an embossed effect to the outlines.