The name of the babysitter for the Parr children is Kari.
Kari McKeen is a friend of the Parr family who babysits Jack-Jack while Helen, Violet, and Dash go to rescue Bob. She confidently tells Helen that her babysitting training has prepared her for the responsibility, though Jack-Jack’s emerging powers quickly make the assignment far more difficult than expected.
Her chaotic evening became the basis of Jack-Jack Attack, a Pixar short released with The Incredibles on DVD. In that story, Kari encounters Jack-Jack’s unpredictable abilities and later mistakes Syndrome for a replacement babysitter. The events add a comic side story to the main film’s climax.
A frequent mix-up is naming a major female character such as Helen, Edna Mode, or Mirage. Helen is Jack-Jack’s mother, Edna designs the superheroes’ costumes, and Mirage works for Syndrome; Kari is the character specifically identified as the babysitter.