Although Wash may not fit the exact archetype of the “manic pixie dream boy,” he does fit a nuanced version of this. Particularly, he displays many of the “nerdy” and immature characteristics that Lambert describes (i.e. he likes playing with dinosaurs as in the clip below).
However, these nerdy tendencies do not harm his work as a pilot. Additionally, Zoe is portrayed as being in control of the relationship and Wash is portrayed as merely supporting her (especially because he is below her in the command structure of the ship).