To caricature is to exaggerate. It is easy to digitally exaggerate the idiosyncrasies of a person's face simply by distorting the pixels using Photoshop's liquid filter or KPT's Goo/Super Goo. For people without photoshop there are many standalone applications such as Caricature Studio. To further parody the subject you can replace the body with one that is markedly different from their own. In this instance the old man is placed on a young muscular body. The head size is disproportionate to the body in order to maintain the cartoon nature of the treatment. We are not aiming to convince the viewer that the body really does belong to the head as this would conflict with the parody that we're trying to create. This treatment is in keeping with the traditional fairground photograph in which the subjects poke their heads through a hole in a board to place themselves on the painted bodies of sailors, muscle-men, busty beach babes, mermaids and so on.