"Phew. I was so worried, Nigel..."

– Katie in Operation: U.T.O.P.I.A.

Katie is a sweet-natured, cheerful and playful girl with brown hair and vivid green eyes, residing on a paradise where kids eat candy for meals and watch cartoons all day. She and Numbuh 1 have a great time in Operation: U.T.O.P.I.A. before the latter finds the loophole in Chester's world, revealing her as an avatar simulation of Chester, her head transformed into Chester's before attacking him. But Nigel activates his J.E.T.A.B.O.O.T.S. and flies away from Katie and her illusions.

Trivia

• She bears a resemblance to Sally Sanban, Numbuh 1's cousin, some blonde-haired background character, some brown-haired background character, the gothic/goth Numbuh 3 and Henrietta Von Marzipan. Coincidentally, her voice actress, Tara Strong, also provides the voices of Sally Sanban in Operation: F.U.T.U.R.E..
  • Katie is also similar to Kairi from the first Kingdom Hearts game, as they are both islander girls in pink who appear on island paradises where only children visit.