Either, "I speak Horse. He’s called Susan and he wants you to respect his life choices" or "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective view point. It's more like a big ball of...wibbley wobbly...timey wimey.....stuff....."mrgreen
"There was a war. A Time War. The Last Great Time War. My people fought a race called the Daleks, for the sake of all creation. And they lost. We lost. Everyone lost. They're all gone now. My family. My friends. Even that sky. Oh, you should have seen it! That old planet... The second sun would rise in the south, and the mountains would shine. The leaves on the trees were silver, when they caught the light, every morning it looked like a forest on fire. When the autumn came, a brilliant glow though the branches..."
(Any time with the Doctor reminiscing about Gallifrey makes me teary-eyed)
Or that bit from The Family of Blood:
"He never raised his voice. That was the worst thing — the fury of the Time Lord. And then we discovered why — why this Doctor, who had fought with gods and demons, why he had run away from us and hidden... he was being kind. He wrapped my father in unbreakable chains forged in the heart of a dwarf star. He tricked my mother into the event horizon of a collapsing galaxy to be imprisoned there, forever. He still visits my sister, once a year, every year. I wonder if one day he might forgive her, but there she is. Can you see? He trapped her inside a mirror. Every mirror. If ever you look at your reflection and see something move behind you just for a second, that's her. That's always her. As for me, I was suspended in time and the Doctor put me to work standing over the fields of England, as their protector. We wanted to live forever. So the Doctor made sure we did."
"We're all basically primeval slime with ideas above its station." ~ Fourth Doctor in "Full Circle"
"So this is what you've been doing with UNIT funds and equipment all this time." ~ Brigadier in "The Three Doctors"
"The Master killed my stepmother, and then my father, and now the world that I grew up in. Blotted out forever." ~ Nyssa in "Logopolis"
"A McCrimmon never died without a fight yet!" ~ Jamie in "The Mind Robber"
"One day I shall come back. Yes, I shall come back. Until then, there must be no regrets, no tears, no anxieties. Just go forth in all your beliefs and prove to me that I am not mistaken in mine." ~ First Doctor in "The Dalek Invasion Of Earth"
"One for casual, one for best." ~ Romana in "Destiny Of The Daleks"
"There's nothing "only" about being a girl." ~ Sarah Jane in "The Monster Of Peladon"
"I thought I'd join up with the Doctor and see the Universe. Where are we?" ~ Adric in "State Of Decay"
"Why don't you pander to my old-fashioned, Medieval superstitions and take them [aspirin] for me?" ~ Barbara in "The Web Planet"