A cat lover, Horitomo has produced a delightful series of prints called "Monmon Cats" (which I believe simply means tattooed cats or perhaps "cattoos"). Some are whimsical and some are fierce. Indeed, some are so fierce that people call them "Yakuza Cats" (after the notorious Japanese mafia-style gangsters).
Of course, Horitomo also tattoos his cats directly on clients --
And here is the artist himself, with a non-tattooed friend --