The official design was chosen by online voting amongst the nine candidates seen here[1]. After a close-run vote, Call F was chosen as the final design.
In the first round, there was an online poll open to everyone. Voters were allowed to cast a single vote for their favorite Call. The poll ran from September 27 to October 1, 2013, the end of the Mighty No. 9 Kickstarter. The top three vote getters would then move onto a second round.
The vote results were announced during a livestream here at around 2:15:00.
The results were also recapped in the Kickstarter post here. Of the over 82,000 votes, the finalists had the following vote shares:
Call H - 10.12%
Call E - 24.09%
Call F - 35.31%
After announcing the results during the livestream, they also talked about other Call designs. This included Inafune's Call D.
(At 2:20:50) Host: One thing that a lot of people pointed out was this hairstyle looks like a certain bad, other villain from a previous game series and might have had a bad association with some people.
(Translator conveying this to Inafune)
Inafune: (laughs) Dr. Wilyという！
Another Translator (Mighty No. 069): He's saying, "Just shut up and say 'Dr. Wily'!"
Host: I was trying to be tactful about it.
Mighty No. 069: "Shut up and say, 'Dr. Wily!'"
Host: Was that on purpose or was that...
Inafune: Dr. Wilyを出さないじゃん。Dr. Wilyを出すべきだと思って、あの、一応silhouetteになった、Dr. Wilyになるから
Mighty No. 069: So, ultimately I was thinking that, you know, there was no Dr. Wily in the game, but there should be somebody that carries the torch, that carries on the torch for Dr. Wily, so, you know, I figured that I couldn't really use Dr. Wily. However, the silhouette looks somewhat similar so that's kind of a way to...
Inafune: <some Japanese>
Mighty No. 069: So probably the high-level people, the high-level people with true art taste, would be able to look at this and know that this truly is the best design. The other people probably just chose F, the ones that didn't know. He's joking folks, he's joking.
Second round
In the second round, voting was restricted to online backers. The results were announced here.
