In June of 2011, CRYSTAL HARRIS bailed on HUGH HEFNER five days before their wedding. But Hugh took her back earlier this year . . . and now, they're engaged again.
--TMZ says they're getting married at the Playboy Mansion on New Year's Eve.
(--I still can't believe Hugh took this woman back. Especially when she went on "The Howard Stern Show" a month after leaving and said she wasn't turned on by Hugh and he ONLY LASTED TWO SECONDS.)