A pair of adorable but fearsome ninja girls. You can tell them apart easily by noting tha Kat has a single, erect ponytail while Ana has pigtails. According to in-game dialogue in WarioWare: Touched!, the two are sisters.
Late one night, a skeletal samurai demon named Boneheads descends on the local pagoda and possesses its owner - who is, of course, you. Immediately, Ana and her band of ninjas rushes to dispatch Boneheads, but the demon makes quick work of them, tying Ana up and leaving her hanging. Ana's only hope is her messenger bird, Don, with whom she sends a note: "Ninja girl, save me!" The recipient is her friend Kat, who then travels from her homeland - which looks a lot like Japan but couldn't be, because Japan shouldn't exist in Wario's world - to kill Boneheads and free Ana.
Kat and her dog, Paw, enter the pagoda and the player can begin Kat and Ana's series of nature games. Like the rest, they're strange, so be prepared to play a snail trying to eat a leaf or a cute little girl with a watering can trying to hydrate a potted flower.
When victorious, players get to see Kat's dog transform into a might blade, which Kat uses to cleave Boneheads into pieces. She and Ana then go for a well-deserved snack at the gelateria. Later, players can also unlock a special game featuring the two ninja girls: Jump Forever. In it, players Wario must jump over a jump rope as Kat and Ana, dressed in kimonos, turn it more and more quickly.
The twosome appear again in WarioWare: Twisted. Their game set, Tap Out, demands the player to make subtle movements with the Game Boy Advance will simultaneously tapping the A button. Kat and Ana's cut scene story involves them straying from the group during a Ninja Elementary School field trip. Kat happens onto a bee hive, which chase both girls into an abandoned cabin, whereupon they are ambushed by an angry goblin. Soon enough, Kat and Ana's respective pets tumble into the cabin and KO the goblin, installing just enough of a false sense of security for the girls to step outside - and once again into the swarm of bees, which chases them back to Diamond City.
More hijinks abound in WarioWare: Touched!, as the girls chase down an apparent banana thief. With Shadow and Shuriken in tow, the girls corner the person who stole Ana's bananas: a cute monkey. The girls gush and decided to name the simian "Numchuck" and take him home. This little storyline gives way for Kat and Ana's microgames, which are grouped under the title "Ninja Scribble." Appropriately, all of them require writing-type movements with the Nintendo DS stylus.
Incidentally, Kat and Ana's names together form the word "katana," a traditional Japanese sword.