Donna: I'm not coming with you. I've been thinking. I'm sorry. I'm going home.
The Doctor: Really?
Donna: I've got to go.
The Doctor: Well, if that's what you want. I mean, it's a bit soon. I had so many places I wanted to take you. The Fifteenth Broken Moon of the Medusa Cascade, the Lightning Skies of Cotter Palluni's World, the Diamond Coral Reefs of Kataa Flo Ko... Thank you. Thank you, Donna Noble. It's been brilliant. You saved my life, in so many ways. You are... You're just popping home for a visit, that's what you mean.
Donna: You dumbo.
The Doctor: Then you're coming back.
Donna: Know what you are? A great big, outer-space dunce.
~Donna and The Doctor, Doctor Who - The Sontaran Stratagem