We all like pie.

Disassociative Identity Disorder is the modern name for multiple personalities, a psychiatric condition disproportionately represented in bestsellers and made-for-TV movies as compared to other psychological diagnoses. DID was extremely fashionable in the '80s and early '90s; today it is much less trendy. There was professional rivalry to see who could diagnose the most “alters,” as the extra personalties were called. This resulted in incredible personality inflation, from the three faces of Eve to a chart-topping 4,500. I may very well have a few myself, but it's hard to tell since they seem to be absolutely identical in every way.