Eventually, the Doctor began to enjoy his travels through time and space, taking people along for the ride and was always reluctant and sad to see them go, even when he knew it was for their own good. The Doctor's personality mellowed around the time of the serial "Marco Polo", and he evolved into the more familiar grandfatherly figure that children loved. The initially irascible and slightly sinister Doctor quickly mellowed into a more compassionate figure. He was protective of the young women he took on as companions; they reminded him of his granddaughter, Susan.