Amy knows a thing or two about kisses. After all, she was a kissogram.
She prides herself on being able to tell what kind of kisser someone is within the first minute of meeting them. Do they smell like breath-mints? Nervous. Do they play with things in their pockets? Groper. Do they lick their lips? Desperate.
It applies to couples, too. Does he keep his eyes on the exits? They're over. Does she clean off the lipstick with a thumb? They're married. Do they laugh when they get it wrong? They're forever.
Though, of course, there are still those who surprise her.
Turns out, River's a groper. Amy had seen that coming. From the Doctor's squeak, she's pretty certain he didn't.
One moment, the Doctor and Rory are fighting over the morality of setting up a minor blast charge in the hospital. The next, River yanks the Doctor by his braces and is kissing him as if a small planet depends on it. Amy tries not to be offended when he doesn't fight it like he did with her. After a small hesitation, the Doctor shoves his hands in River's hair and kisses her back. River makes a sound that suggests he pulled hair. He draws back, wearing his apologizing face. That's when River gropes his bum. He squeaks. She laughs. They're kissing again. River steps on his foot but he doesn't seem to notice or care. They both fall back against the side of the building. That has to have hurt.
Amy's enthralled but of course, Rory is uncomfortable and has to go and ruin it. "Hate to interrupt," he says, "but we have a bit of a situation on our hands."
River's the one to end the kiss, leaving the Doctor looking disheveled and confused. He has a bit of her lipstick above the corner of his mouth. She smudges it away with her thumb. "Right," River says. "That should get us into the hospital."
"What hospital?" the Doctor asks and Amy's grin starts to fade. He stumbles into River and they both laugh as she holds him up.
"What did you do to him?" Amy asks.
"Hallucinogenic lipstick." River grins wide like she does at memories. "Oh, he's going to seethe when he works this through his system. Sorry, sweetie."
"Hallucinogenic lipstick doesn't work on Time Lords," the Doctor informed them before nearly falling over. He squints his eyes at Amy's husband. "Rory has your nose always been that big?"
"You drugged him," Amy says as the Doctor giggles at something only he can see.
"Yep." River pushes the Doctor back onto his feet and motions for Rory to help her. "Now, I think this man needs a doctor. Shall we?" She flashes her mad grin again and Amy can only marvel. Drugged kisses, that's a new one.
"Don't worry, sweetie," River whispers to the Doctor as they lead him into a hospital with cat people as nurses. "We'll all laugh about this later." She looks at him a little closer. He hums happily. "Much, much later."