*raises hand* David Tennant is right, his name is "The Doctor", but it's not wrong to call him "Doctor Who". Doctors One through Nine are called "DOCTOR WHO" in the credits! In fact, other former Doctors refer to him as "Doctor Who".
Which line is originally taken from Arthur Weasley in HP when he asks Harry "Maybe, since you were raised by muggles, you can help me. What exactly IS the function of a rubber duck?" People who quote HP ftw