“Amy sat back and grinned. "You just smiled." That was definitely something else she could get used to.Of course, he frowned immediately. "I smile.”
“Amy Pond: 'I thought... well, I started to think you were just a madman with a box.'The Doctor: 'Amy Pond, there's something you better understand about me, 'cause it's important and one day your life may depend on it. [He Smiles] I am definitely a madman with a box.”
“Life is a mirror: if you frown at it, it frowns back; if you smile, it returns the greeting.”
“He grinned lightly at me and I smiled back. Lord I loved this man. His smile was as bright as the sun.”
“I could really use someone else's smile today.”
“I could not, of course not, not smile at you.”