Kat and Kit were born to a humble farmer and his wife, and became older siblings to a second pair of twins. It was from their father they learned of the the city of treasures, El-Dara, from his book. One day shattered their lives - When their father was harvesting and took a break to picnic with his family, a twister was fast approaching. Kit and Kat's mother and their little brother and sister made it to the shelter but a large tree barred Kit, Kat, and their father. He got them over and told them to keep running and not look back. They made it in time to watch as the twister swept their father away to his death.
Without her husband to do the harvest, Kit and Kat's mother had to do it herself and could barely prepare enough food for all four of her hungry children and not enough for herself. Kat soon convinced Kit they should leave and find the lost city of El-Dara so their mother could feed their little brother and sister.
They ran away to Thundera hoping to find information of their goal. Instead, they found only deaf ears to their pleas for spare change and food. They bumped into a man who dropped his coinpurse, and considered stealing it but decided to return it. However, when they tried to, the man immediately accused them of being thieves, forcing them to run and hide. Out of desperation, they eventually decided they'd have to do whatever it takes, and began stealing to survive.
WilyKat uses his words to distract, while WilyKit uses her musicial instrument to hypnotize them. WilyKat then steals food and money from people. Both he and his sister dream of someday saving up enough money to go and find a map that will lead them to the lost city of gold and riches, El-Dara, where he said "cats will be begging us for money."
Like his sister he loves eating candy. It is difficult to tell who is more mature of the thunderkittens as WilyKat seems to be the one responsible for ideas since he tells his sister to leave the house so that his mother and younger siblings get more to eat. Kat seems to be the one who talks for the kittens as he is the one who convinces Lion-O to let them join the older three cats. Kat's maturity is also shown when he promises his sister to take her to El-Dara. Kat seems to be slightly braver as he shoots down a Warbot and in Survival of the Fittest he hits a huge creator. WilyKit seems to show maturity as she cautions Kat from stealing (although she also starts stealing later) and starts to meditate with the elephant when they were attacked. She is the one who believes that Lion-O would be alive. At the end of the first season she convinces Lion-O to see what he gained (uniting most of Third Earth's animals under Lion-O's leadership).
WilyKat wears clothing that is adorned with multiple pouches and pockets, much like his sister. These presumably aid in his thieving. Like many of the other cats clothing, his outfit is asymetrical, having only one glove on his left hand. He occasionally wears a cloak. Like the other cats, he wears footwear that only cover the tops and insteps of his feet. His overall appearance is one of being poor, as his outfit is simple, and doesn't function as armor, as most of the other cats clothing does.
WilyKat is a skillful pickpocket like WilyKit, using his sister's music to take advantage of a distracted target. He can also increase his speed and agility temporarily as a result of entering a sugar rush caused by eating Candy Fruit.
WilyKat's usual weapon is a Flank, a retractable reel of string or wire attached to a ring with three claw-shaped ornaments that he normally uses in incapacitate opponents or to reach high places. On occasion, WilyKat can use his Flank as a musical instrument by strumming it like a string instrument - such as a guitar or an uproght bass - while holding the wiring down with his foot and raising the item above his head. During the second half of the first season, WilyKat gained both a hoverboard and the Forever Bag, the latter he shares with WilyKit. He also keeps the map of El-Dara.
- The Sword of Omens (episode)
- Ramlak Rising
- Song of the Petalars
- Old Friends
- Journey to the Tower of Omens
- Sight beyond sight
- The Forest Of Magi Oar (episode)
- Into The Astral Plane
- Between Brothers
- New Alliances
- Trials of Lion-O, Part 1
- Trials of Lion-O, Part 2
- Survival of the Fittest
- The Pit
- The Forever Bag (Episode)
- The Soul Sever (appearance only)
- What Lies Above, Part 1
- What Lies Above, Part 2
- Kat and Kit used the "Innocent Kitten" look in an attempt to join the three older Cats.
- The production crew has explained that their tails were to help with their acrobatics and agility, but also introduced them as a birth defect and a "social stigma."
- You can't see either Kit or Kat's ears because their whole "hairstyle" is their ears.
- Kat, might seem the leader of the ThunderKittens but this is shown very slightly and very rarely. It is a possibility that it is not true.