While in high school, Johnson was a member of an award-winning student-produced comedy show, Beyond Our Control which ran on the local NBC affiliate, WNDU-TV, at that time owned and operated by the University of Notre Dame.

[1] Johnson earned a degree in radio, television, and film at Northwestern University.

[3] In 1994, Johnson, along with producer Angela Santomero and director Todd Kessler, which Nickelodeon executive Brown Johnson called a "green creative team",[4] created the series Blue's Clues.

[5] According to Johnson, she was cast as the voice of Blue, because out of the show's crew, she sounded the most like a dog.

[4] She is married to Robert Mowen (another Beyond Our Control alum) and has three sons: Thomas, Oliver, and Emmet.