Baby

Alfie Owens, a human baby. (TV: Closing Time)

Babies were what humans and various other species called their young. In general, human offspring were referred to as babies from birth to approximately when they began to walk. According to the Eleventh Doctor, babies had their own language, which he could speak. (TV: Closing Time)

The fleshkind baby, Sky Smith, was primed to rapidly age into a pre-teen upon encounter with the metalkind. (TV: Sky)

The Master's TOMTIT machine once regressed Sergeant John Benton to a baby. When restored to adult form, he appeared before his UNIT colleagues stark naked. (TV: The Time Monster)

A human baby was once converted into a Cyberman. The Cyberman had regular arms but had a tail like a Cybermat. (PROSE: Illegal Alien)

Gifftan babies were born with two umbilical cords that had to be cut simultaneously at birth. Male babies were only born to male parents, whereas female babies would only be born to female parents. (TV: The Tsuranga Conundrum)

In the 22nd century, some genetics labs artificially grew human babies on which to experiment. The Seventh Doctor and Ace stole one of these babies to act as a host for the Timewyrm. (PROSE: Timewyrm: Revelation)