I recently took part in a caricature contest on the internet. The assignment was 'Cillian Murphy'. This was my entry. I created the base in Character Creator. This means that I picked out a realistic model and then used sliders to get as close as possible to what I had in mind. Hundreds of sliders! To drive you crazy! :-)
Then I imported the result into Blender, where I refined it through sculpting, cloth modeling, hair creating, framing, adjusting materials and lighting to the final result. And finally a little retouching in Krita.