3.
He hasn't gotten sick in three hundred years.
Timelords don't usually catch viruses from others. In fact, the immune system of a timelord usually repels bacteria like no other system in the universe.
However, sometimes, once in a blue moon, he catches something, some bug floating around the atmosphere.
Of course it happens while he's with River.
Three hundred years, and his immune system picks now to go off for a pudding break?
Of course.
She brings him some soup and tea and quite a lot of tissues, makes sure he's comfortable in his bed.
It's wildly domestic, and he can just tell how much fun she's having, playing house.
It's just a cold he's diagnosed himself with. Stuffed nose, sore throat, slight fever. All symptoms of the most common human illness in the book.
Still, she makes him rest.
"Darling, when you're ill, it's much easier for infections to spread." She explains as if he's a child, while cleaning the dirty tissues from his bedspread. "Weakened immune system, remember? Especially timelord immune systems. Those are a difficulty."
"I know, River." He grumbles, holding back the instinct to roll his eyes because this is ridiculous and he is fine and he should be able to do things when he has a cold.
She looks pointedly at him, crossing her arms and raising an eyebrow.
"I know that tone." He raises his eyebrows too, matching her indignant look. "You may think you're invincible, but you need a rest just like every other being in the galaxy."
"Not every other being." He grumbles, and she rolls her eyes, going back to fetch the rest of the phlegm-infested tissues from the mattress. "It's just a cold. A tiny human cold. I'm sure I can get up and walk arou-"
And suddenly he's accosted by a sneak cough attack.
Brilliant way to prove a point.
When he's finally managed to stop coughing, throat burning and cheeks flaming red, he sees her, offering him a mug filled with water. She's definitely smirking, like she always does when she's proven somewhat correct.
He both loves and hates that expression.
"Thanks." He mutters, accepting the mug and taking a sip of the crisp, cool water. She sits sideways on his bed, her eyes tender despite the smirk on her mouth.
"It's alright to take a break sometimes." She takes his hand in both of hers. "How about, just for once, you let me take care of you? Just for another day, I promise. I'll be surprised at how much better you'll feel." She leans forward so their noses are almost touching, placing a hand on his cheek. "Just relax."
He almost smiles, then.
He hates being babied as much as she does. Always has, always will.
But being babied by River, he's decided, could be a whole lot worse than the treatment he's getting right now.
"Fine." She smiles too, a real, genuine smile, and presses her lips to his forehead.
"Good." And she pulls back, keeping one hand on his. "I promise, the next time I get sick, you can serve back exactly what I'm doing to you."
"River, you never get sick." She bites her lip, and he smiles, really smiles.
"Well, Doctor, neither do you."