Things you can dress up as beginning with r?

There are a few things that come to mind: Fireman, Firewoman, Flight Attendant, Fairy (and variations on this theme such as fairy queen, fairy princess and so on), flapper (a 1920s costume), a First Lady, French Maid, Fortune Teller or Formula 1 Driver.

Famous characters include: Father Christmas, Frank N. Furter (Rocky Horror), Freddy Kruegger, Fred Flintstone, Fiona (from Shrek), Fred (from Scooby Doo), Flash Gordon, Foxxy Cleopatra or Felicity Shagwell (from Austin Powers), Friar Tuck.

Famous people include: Florence Nightingale, Freddie Mercury, Guy Fawkes and so on; there are probably many more but not sure how much anyone would be recognised dressing up as Michael J Fox or Colin Farrell for example!