Reddit user CalicoDan shared a squad of Warhammer 40K’s Spaces Marines customized with great talent to look like Dragon Ball characters Goku, Krillin and the Turtle Hermit.
A lot of custom models, including those, make extensive use of “Green Stuff” to sculpt new details or even completely modify a figurine. It’s a modeling epoxy that is easy to work with if you have the right tools, and is very affordable.
I have personally used the Green Stuff from Army Painter (not sponsored) and I can recommend it, but most others will work just as well. When it comes to learning how to use it, the small YouTube channel Last Light Creative has been a great resource for me.