FernGully: The Last Rainforest (1992)

Crysta is a fairy of curious nature who lives in FernGully, a pristine rainforest free from human intervention. The fairies of FernGully once lived in harmony with humans, but believe them to have gone extinct after having been driven away by a dark spirit named Hexxus. Crysta is the apprentice of Magi, a motherly-figure fairy who imprisoned Hexxus in a tree. One day Crysta explores a new part of the forest and meets Batty, a Megabat who claims to have been experimented on by humans, giving him a cocky and unstable personality. However, fairies refuse to believe him, except for Crysta, who volunteers to investigate the situation. She sees Zak, a young lumberjack whom Crysta accidentally shrinks when she tries to save him from being crushed by a falling tree, though does not know how to restore him to normal size.