In fact, as their existence is theoretically impossible there has to be a genetic anomaly for a male cat to be a calico cat. The male calico cat is described as “very rare”. They are nearly always sterile because they have XXY chromosomes. This causes a condition called Klinefelter’s syndrome (in people), which is the result of additional X genetic material in males. In people, this syndrome can cause the person to be taller than usual with less muscle control and weaker muscles. I wonder if it affects cats in the same way. Update: please see Sarah Hartwell’s comment. The main cause of tortie male cats is a thing called “chimerism”. This is when two fertilised eggs fuse to become a single kitten. I’ll ask Sarah Hartwell to explain it in an article! There is a link to her site in the comments.
As they are very rare they are possibly more valuable than a typical pedigree cat if they are a pedigree cat. However the sterility prevents breeding, devaluing the cat.
Calico” is an American term meaning tortoiseshell and white. In the UK cat fancy the word “calico” is not used as far as I am aware.