On screen, the Eleventh Doctor's ongoing companions were Amy Pond, Rory Williams, Clara Oswald and River Song (though River's travels with the Doctor were sporadic and mostly said to be off-screen). Other characters have been implied to have been companions though this isn't confirmed, including Riddell and Nefertiti ("Dinosaurs on a Spaceship") and Madame Vastra and Strax ("A Good Man Goes to War"). And there is also the special case of "Sexy," a.k.a. The TARDIS ("The Doctor's Wife". The comic books and novels have featured additional companions.