Looking back on four decades of "Saturday Night Live" impersonations, it's cool to see how many ways a celebrity impression can be hilarious, provocative, or just plain effective. Sometimes an impression works because it's a dead-ringer for the real thing (See: most of Dana Carvey's work), but sometimes a twisted or loopy take on a familiar figure is even more engrossing and funny.  We've picked the 25 best celebrity impressions in "SNL" history, and for the sake of such a short list, we're only including impersonators who served as cast members on the show. (This means Kate Hudson as Drew Barrymore and Tom Hanks as Dennis Miller will have to wait for another list.) I'll start the countdown by acknowledging the 10 candidates who almost made the cut but just missed: Terry Sweeney as Nancy Reagan, Jan Hooks as Tammy Faye Bakker, Kristen Wiig as Suze Orman, Jimmy Fallon as Barry Gibb,...