Something that I learned at uni the other week - there's a parasite called Toxoplasma Gondii, which up to 1/3 of people in the world carry and it has some really random effects like... *drumroll* it makes you like cats!!
It depends on your gender! " infected men like the smell of cat pee—or at least they rank its scent much more favorably than uninfected men do. Displaying the characteristic sex differences that define many Toxo traits, infected women have the reverse response, ranking the scent even more offensive than do women free of the parasite."
Fascinating stuff. A line of research that is just getting started. The U.S. Centers for Disease Control say 22.5% of the U.S. population is infected.