Pownall and Heflick (2023) investigated gender stereotypes in all 47 Mr Men and 34 Little Miss books. One of the studies asked (adult) participants to rate the masculinity/femininity of the character names on a scale from 1 (“entirely feminine”) to 5 (“entirely masculine”). The “Mr” and “Little Miss” were stripped off, so, e.g., participants were asked about the word “Quick”, “Princess”, “Greedy”.
I created a name binariness index for each mean rating, \(r\); the distance between the mean rating and 3 (the mid-point), as a proportion of the maximum that distance could be (2):
\(\displaystyle \frac{|r-3|}{2}\)
Here’s a plot of the names, sorted by name binariness. So good candidates for nonbinary characters would be Mx Quick or Mx Lucky. Alternatively, you could rightly reject the premise that any of them are gendered and go for Mx Princess.
References
Pownall, M., & Heflick, N. (2023). Mr. Active and Little Miss Passive? The Transmission and Existence of Gender Stereotypes in Children’s Books. Sex Roles.