Anonymous1: Vivian's already a boy. This isn't Rule 63. Vivian is stated as a boy in the Japanese version, but they never give any mention to Vivian's gender in Western translations. Vivian is a transgender boy, so this isn't Rule 63 and doesn't deserve such tag.
Anonymous2(1): @GrandMasterToadette: In the Japanese version of Paper Mario: The Thousand-Year Door, Vivian was depicted as a male who identified as a female. It is openly stated in Vivian's character description, which is translated as "One of the Shadow Trio, Vivian appears to be a girl but is really a boy."
-Mario wiki
bluesgthawk: @GrandMasterToadette: In the Japanese version of Paper Mario: The Thousand-Year Door, Vivian was depicted as a male who identified as a female. It is openly stated in Vivian's character description, which is translated as "One of the Shadow Trio, Vivian appears to be a girl but is really a boy." (in Japanese: 「カゲ三人組の一人だった オンナのコのようで ホントは オトコのコ」). Additionally, Goombella's Tattle reads: "That's Vivian. Of the Shadow Trio, she's the youngest sister... er, brother." (in Japanese: 「『ビビアン』よ カゲ三人組の一人で いちばん下の妹 ・・・じゃなくて 弟ね」). While Beldam uses the term "majotachi" (meaning a group of sorceresses) to refer to her, Marilyn and Vivian as a collective, she also objects to Vivian trying to call the collective 「カゲ三姉妹」 Kage Sanshimai, the "Three Shadow Sisters", correcting the name to the gender-neutral 「カゲ三人組」 Kage Sanningumi, the "Shadow Trio", reminding Vivian that she is an 「オトコ」 otoko, "boy", written in red katakana for emphasis. However, in the end, Goombella's letter indicates that Vivian's choice to be identified as female is accepted by her sisters as part of their efforts to be nice to her after the events of the game.
-Mario wiki