I’ve rewatched Wall-E at least 6 times but I think a (not really that small) design decision that was fascinating about this film was the distinguished shapes between ‘new’ and ‘old’ machines/technology.
WALL-E is a boxy (rusty) old ‘outdated’ with sharp edges, compared to EVE who’s super sleek and chic with curved edges, when all her limbs (and head) are retracted, it creates a seamless silhouette.
This transfers to the other robots in the film as well, such as the rogue robots which all have rounded edges even though they’re not necessarily spherical.
I’m pretty sure the differences between WALL-E and EVE are intentional to help with marketing purposes (easier to distinguish, sells the whole star-crossed lovers ish narrative) but it’s pretty cool that smooth edges are somehow associated with the future.