The following characters are not protagonists in the series, and some do not even belong to the Joestar bloodline. However, it is notable that their names are able to be shortened as "JoJo":
The name "JoJo" originated at a Denny's where Araki and his first editor, Ryosuke Kabashima, had their first meeting pertaining to the series. The two had decided on "Jonathan" as the series' protagonist, however, Araki also wanted the initials to match in a way similar to the American filmmaker, Steven Spielberg (S.S). They eventually landed on the name, "Jonathan Joestar" (J.J) and thus the nickname "JoJo" was born.
Jonathan was rumored to be named after "Jonathan's Family Restaurant," however, both Araki and Kabashima confirm this was an urban myth that formed among fans back in the day. Araki had also brought up the name during a 2006 interview, but he claims the interviewer had mentioned it and he just went along with it by accident. Coincidentally, their later meetings during Parts 2 and 3 were held at said Jonathan's restaurant.
- Giorno Giovanna and Josuke Higashikata (Part 8) are the only main protagonists who were never referred to by the nickname "JoJo" (or the stylized "GioGio") by other characters in canon works.
- The only time the stylized "GioGio" is mentioned by another character is during the ending scene of the light novel Purple Haze Feedback wherein Pannacotta Fugo and Giorno Giovanna discuss the events of the story. Giorno tells Fugo to "do him a favor" and call him "GioGio" instead of "Boss", Fugo replies by swearing his allegiance and refers to him as "GioGio".
- The kanji suke (助) has an alternate Go-on reading as jo.
- Giorno Giovanna (ジョルノ・ジョバァーナ Joruno Jobāna), due to phonetic similarities between the Italian syllable "Gio" (dʒo) and the Japanese syllable "ジョ" ((d)ʑo). Can also be GioGio.
- George Joestar (ジョージ・ジョースター Jōji Jōsutā)
- The kanji sada (貞) has an alternate Kan'yō-on reading as jō.
- The kanji shizuka (静) has an alternate Go-on reading as jō.