Osgood

Played by Ingrid Oliver

"You're a credit to your species, Petronella Osgood"

Petronella Osgood is an enthusiastic young scientist who works for UNIT. Her dedication to her work is second only to her devotion to the Doctor. Her attire often reflects her admiration of the Time Lord, sometimes wearing a long scarf or a bowtie or even question-mark lapels to reflect the wardrobe of various regenerations of the Doctor.

As a Scientific Advisor for UNIT, Osgood has helped the organisation face off against multiple otherworldly threats, and is pivotal in maintaining the brokered peace between humanity and Zygons. As an enthusiast of the Doctor's adventures, Osgood is also perfcetly suited to maintain and curate UNIT's mysterious Black Archive.

As a distant superfan, Osgood finally gets to meet the Doctor when Kate Lethbridge-Stewart takes him to the National Gallery to investigate several paintings that have been smashed from the inside. Keen to impress the Doctor, Osgood proves herself to be resourceful, tripping up a Zygon with her scarf to escape from its clutches. Osgood and a Zygon duplicate help broker peace talks between the species.

Later, Missy murders one of these Osgoods, but the surviving one refuses to reveal whether they were Zygon or human. Briefly, this Osgood becomes a target of a rogue Zygon group who believe she has betrayed their species.

In the end, the leader of the Zygon group not only abandons their antagonism, she transforms her appearance into that of Osgood. Both of these Osgoods then dedicated themselves to defending the Earth.