An adult prom is a social event that is almost perfectly similar to a high school prom in terms of themes and attire, except that some adult proms also serve alcoholic beverages, and therefore most adult proms (at least in the U.S.) require those attending to be at least 21 years of age. The origin of adult prom is unclear, though Drew Barrymore is often credited with inadvertently inventing the concept in the 1990s, when she stated in an interview on "Late Night with Conan O'Brien" that she threw a prom party for herself and a few friends who never got to go to prom.