Basic Trope: Animal characters appear and act completely humanlike.
Straight: Leo the Lion stands on two legs and talks with the other human characters and is treated no different than the rest.
Exaggerated: Leo the lions wears clothes including pants and shoes, owns his own shop, is a highly respectable citizen in his mostly human town, and is never ever referred to as a lion nor ever shows any lion like behavior.
Leo is an alien that appears like the Earth lions but has evolved to a humanlike form.
Or, Leo comes from a race of creatures that evolved from lions to become more humanlike.
Or, Leo started out as a lion who has been genetically altered to resemble humans.
Or, Leo was a pet project of somebody.
Humanity Is Infectious gives some physical aspects as well as mental to those undergoing it - walking on two legs and changing front legs applies among them, and Leo learned human ways of being while still a lion.
Double Subverted: Until he stands up on his hind legs and greets his friends in human speech.
Parodied: Leo the Lion appears and acts like the other human characters, but the human characters still insist on treating him as a lion, making lion-themed puns, and asking Leo to perform circus tricks.
Zig Zagged: Leo the Lion appears and acts like all the human characters, but has a pet dog, Fido, who acts like a regular dumb dog. Down the street, Leo's friend Kerry Koala lives. Kerry has the appearance of a regular koala, but can speak English and does human things as well as koala things. Kerry also has a pet dog, Sandy, who acts just like a regular dog, but can also speak. Things only get weirder from there.
Averted: All animals appear and act like normal animals.
"We need animal characters to keep the kids happy, but we need them to do human things to make them relatable."
Deconstructed: Leo is a talking lion that acts human, but is still forced to live in a cage at a zoo and is forced to perform demeaning tricks for the humans. He begs to be released and treated like a normal human, but is constantly told by the zookeepers that he's just an animal and doesn't have the same rights as the humans. He eventually goes mad hearing this and escapes and goes on a murderous rampage, killing hundreds. He is eventually sedated and put to sleep by animal control.
Reconstructed: Leo's race has evolved from lions to a human like state. Humans, realizing that Leo and his race are no different than them, decide to give them human being status and give them the same protection under the law that humans get. Leo learns the ways of the humans and becomes friends with many of them. Leo learns to wear clothes and hold down a job, eventually buying and owning his own shop and becoming a well respected citizen of his town.