The Doctor's Daughter (played by Georgia "Cutie" Moffett) is the Tenth Doctor's daughter in the show but the Fifth Doctor's daughter in real life. Oh, and it's also the sixth episode of the fourth series of Doctor Who.
The TARDIS takes the Doctor, Martha, and Donna to the planet Messaline. As they emerge from the TARDIS some soldiers force the Doctor to stick his hand into a progenation machine, which uses his DNA to generate a female soldier. Donna names her Jenny because the Doctor calls her a "generated anomaly." Ayy lmao.
She later gets killed but regenerates, or something.
See also: Potential Companions.
Whether or not it was intentional the episode felt designed like it was made to get ratings. Otherwise it was meh.