There's a reason people like schoolgirl or baby costumes; going backward in time to a period of innocence and dependence on others (but with a potentially raunchy attitude) can be really arousing. Halloween is the perfect time to wear a baby costume. "Wear a diaper and pacifier costume," she suggests. Why might this be a fetish? "Some theories include that perhaps [an] infantilism fetish is about regression to a cared-for state," she explains.