Baby

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

Babies were what humans 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)