Mary Catherine (nick named Cathy) was the third born of the Fischer quintuplets. She was named after a Sister Catherine Stephen. Cathy, along with her sister Mary Ann, got to come home from the hospital four days before Christmas to join the rest of the family for the holiday celebrations.
As a baby, Cathy was described as "the greatest giggler, who starts laughing the minute anyone goes into the nursery, or even when just lying by herself." As a toddler, she was a bit more shy than the other four.
As a young adult, Cathy worked in a daycare center for a while, and had an interest in photography. She enjoyed playing softball out in the field and was described as the artist of the group.