Despite her training and optimism, Kari is unprepared to deal with Jack-Jack's emerging powers, and leaves increasingly frantic phone messages with Helen, before Syndrome steps in and introduces himself as a more experienced "replacement sitter". Kari is clearly unaware of Syndrome's checkered criminal past; only asking him why he wears a big "S", to which Syndrome calmly responds that it stands for "Sitter". Kari's ordeal remains off-screen in the film, but serves as the focus of the short film Jack-Jack Attack. She is last seen being interrogated by National Supers Agency government agent Rick Dicker, who asks if she has told anyone about the ordeal. Kari explains that her parents thought she was joking and wishes to forget the whole ordeal, to which Dicker promises that she will as he activates a device to erase her memory of the incident.
Her surname is only mentioned in the screenplay and in Jack-Jack Attack.