Olga

オルガ

She is not exactly a recurring character, but she does have a prototype: a transforming lady robot named Jet, who serves as a supporting character in the minor work Whirlwind Z (Tezuka Osamu manga zenshu:, vol.52. Sempu: Z. Tokyo, "Kodansha", 1978).
In 1979, film critic K. Ono mentioned Jet during an interview with Tezuka, stating that a transforming robot would make for some interesting animation. According to the film's pamphlet, this is how the idea for Olga was conceived.
Olga also makes a cameo appearance in one of Tezuka's later comics, Rainbow Parakeet (Tezuka Osamu manga zenshu:, vol.2 Nanairo Inko. Tokyo, "Kodansha", 1994). Since the title character of the series is, apart from being a thief, an actor, there are many theatre references, and the chapter in which Olga appears is named, uncoincidentally, Waiting for Godot after the surrealistic play by Samuel Beckett. As in the play, Godot (or, in this case, Godo?) himself does not appear. As in the film, Olga is a robot. Everything else is quite different from either the film or the play, with Olga being abused, broken, stolen, and finally drowning in the sea "to wait for Godot for ever". Here is a page from the comic featuring Olga and Parakeet. Many thanks to Yokohama-Kabitan for pointing out the cameo and to OlgaMaster for providing the picture.
Another unexpected cameo was spotted in Otaku-no Video, Gainax's classic satire of anime fans. One scene briefly features a Japanese girl dressed up as Olga standing in the crowd. Many thanks to OlgaMaster for the screenshot - a unique chance to see "Olga" with black hair.