Calypso Jonze
Calypso Jonze was a mixed race, pansexual, trans, non-binary bounty hunter. They came from Io in the 51st century. They met the Sixth Doctor, Flip Ramon and Constance Clarke and accompanied them on their mission to retrieve the Somnifax, a sentient weapon able to make someone's worst imaginings a reality.
When they found the Somnifax inhabiting the mind of 20th century author H. P. Lovecraft, the Doctor left them and Constance to watch over him. Lovecraft was incredibly disrespectful toward Calypso, expecting them to dress as a woman and attacking them with racist slurs like "mongrel". Calypso punched him for this remark and came close to doing worse before being stopped by Constance.
Despite initially planning to return the Somnifax to its creators for the financial reward, Calypso decided after seeing the damage that it wrought that it was better that it wasn't returned and they left it in the Doctor's care. (AUDIO: The Lovecraft Invasion)
Some time later, the Doctor and Constance called on Calypso's services again to transport them to the headquarters of the Freebooters when they threatened an innocent colony. Calypso and Constance managed to rescue the Doctor when he was captured and Constance managed to save them and their ship from missiles by dumping its cargo of drill heads (to Calypso's irritation). They were grateful when the Doctor secretly programmed their ship to track down a secret sixth unit of Freebooter funds as payment for their services.
Calypso held a romantic interest in Constance, who was oblivious to their advances. The Doctor, however, noticed and Constance caught on to the Doctor's insinuations after they had departed, leaving her surprised and speechless. (AUDIO: The End of the Beginning)
Behind the scenes
Jonze is voiced by Robyn Holdaway, who, like their character, is non-binary and uses they/them pronouns.