Mole
Mole is a sensible animal, yet generous and extremely loyal to his friends. He is closest of all to Rat, the animal who teaches him the value of exploration after he leaves his home in the first chapter. Since Mole is an underground animal by nature, his journey into the upper world near the river poses the novel's first main conflict. A 'younger' character than Rat or Badger, Mole serves as our first lens into the story, as he slowly matures from a frightened animal into a self-reliant, brave and clever companion.
Rat
The river animal Rat is kind, sociable, and accommodating. He has a strong sense of manners and responsibility, so he wants to make sure everyone around him feels comfortable and included. Rat prefers to stay near the water because it is his home, but he also enjoys traveling with his friends. Though loyal to all his friends, Rat cares most for Mole, whom he invites to live with him and to whom he acts as mentor. In this way, he is an 'older' animal than Mole is.
Toad
Toad is the flightiest and pettiest character in The Wind in the Willows, due to a combination of immaturity and unrestrained wealth. He represents the British upper class, as he is an aristocrat living in his large inherited estate, Toad Hall, and has a snooty attitude towards those of lower class. The 'youngest' of the animals, he is quick to pick up and then dismiss expensive hobbies, most notably with motorcars. And yet Toad is often described by critics as the novel's most complex character, partly because he also cares deeply for his friends. They in turn worry about his habits, and eventually help him embody a more mature and grounded attitude towards life.
Badger
The 'oldest' of the animals, Badger is a stoic and solitary character who lives in the Wild Wood. While he is friendly and hospitable, caring deeply for his friends, he also eschews proper etiquette as a result of his removed, underground life. Because of both his seriousness and his gruffness, he is the one who works hardest to reform Toad's habits.
Otter
Though Otter appears in only a few chapters of The Wind in the Willows, he is a part of the central friends group. He is quick and bright, and gains the respect of other animals by always being on hand to help when needed.
Sea Rat
Sea Rat, who appears only in Chapter 9, is an animal who has spent his life traveling. Born in Constantinople, he braved the seas until attempting a country life near the Wild Wood. At the time Rat meets him, Sea Rat is preparing to return from sea, and his perspective on life challenges Rat, who was already feeling restless in the midst of a 'mid-life crisis.' For a short while, Rat feels compelled to set off for adventure himself because of Sea Rat's life of freedom.
two young hedgehogs
These two young animals stay with Badger after the snowstorm interrupts their trip to school in Chapter 4. While there, they eat a breakfast and visit with Rat and Mole before leaving with some money Badger gives them.
caroling field mice
These animals visit Mole's home while he and Rat are staying there in Chapter 5.
Portly
This young otter is Otter's son who is missing in Chapter 7. When out searching for him, Rat and Mole find him resting next to Pan.
Pan
Taken from Greek mythology, Pan is a demigod of music and nature. He rescues Portly when the animal is missing, and calls Rat and Mole to Portly through a strange, beautiful song.
the gaoler’s daughter
The gaoler's daughter feels an affection for Toad when he is imprisoned, and hence helps him devise an escape plan involving her aunt the washerwoman.
the jail's washerwoman
This old woman gives Toad her clothing in exchange for money, so that he can escape from jail.
the engine driver
This man helps Toad in his escape from jail, thinking the animal is a washerwoman. Even after he learns the truth, he helps the animal, letting him leap off the train while they are being followed.
the bargewoman
This old woman pretends to believe Toad's lie about being a washerwoman and lets the animal ride with her a while. Once she mocks Toad after he fails at washing clothes, he sinks her barge and steals her horse, showing his immature and ungrateful side.
the peddler
After this man feeds Toad during his escape journey, Toad sells the bargewoman's horse (which he stole) to him. Toad tries to cheat the peddler, who nevertheless demands a fair price.
the sparrows
In Chapter 9, these birds are preparing for their eventual winter move down South. Their plans upset Rat, who wishes they would stay.
the mice
In Chapter 9, these animals are preparing their home for winter. Their plans upset Rat, who fails at convincing them to explore with him.
the weasels and stoats
These Wild Wood animals take over Toad Hall while Toad is in jail. The main group of friends have to devise a secret plan in order to defeat the Wild Wood animals and commandeer the house.
Chief Weasel
This Wild Wood animal leads the weasels and stoats while they live in Toad Hall.