Which animated films under 100 minutes made the biggest structural or visual leap?

Runtime constraints tend to force interesting decisions. A shorter feature has to establish its visual language and narrative logic faster, which sometimes produces more concentrated innovation than a longer film can sustain. Curious whether there are animated films in the under-100-minute range that you think made a more significant formal contribution than their length might suggest. Not just films that are good, but ones where the production method, the way movement was used, or the storytelling structure actually shifted what the medium could do afterward. Are there cases where the brevity itself was part of what made the formal experiment possible or legible?