During the 1980s, Michaelsen played Katie Kanisky on the NBC sitcom Gimme a Break! Her other television credits include guest star roles on Hart to Hart, Full House, and The Incredible Hulk.
During her childhood years, she lent her singing voice to the Sesame Street soundtrack and performed in several Off-Broadway productions.
She was educated at Beverly Hills High School and the University of California, Los Angeles.
Born Kari Markussen, she grew up in New York City and Los Angeles as the daughter of singer Arne Markussen and dancer Roberta Stevenson. Her seven-year marriage to David Waldock produced a son named Nickolas.
She co-starred with Nell Carter on Gimme a Break!