an urge

addiction

mysophobia

eccentricity

bad habit

exhibitionism

Munchausen syndrome

onychophagia (nail biting)

necrophilia

(sexual) fetishism

pedophilia

foot fetish

transvestism

pica (medicine)

indecent exposure

lit. cut sleeve (idiom); fig. euphemism for homosexuality, originating from History of Western Han [[漢書|汉书]]: emperor Han Aidi (real name Liu Xin) was in bed with his lover Dong Xian, and had to attend a court audience that morning. Not wishing to awaken Dong Xian, who was sleeping with his head resting on the emperor's long robe sleeve, Aidi used a knife to cut off the lower half of his sleeve.

foot fetishist

to have strange and dangerous addictions (idiom)