Are you sure it's not done the ol fashion way, hand drawn? If not, it looks like a decent draw program and a graphics tablet.
If you are sure it is an effect, I've seen ads for picture to cartoon places but that's all I know. Well, since I don't think anyplace like that would exist, it would have to have been 'tuned up' after something like that anyway.
Looks like art to me! (but I'm certainly not an artist.)
Good Luck! (And good idea asking, I've wondered for years how they make the 'Magic Eye' pictures.)
-mud