The Doctor had a book and a determined glint in his eye.
"Birds do it," he wheedled, pouting at her from across the console. "Bees do it. Even educated fleas do it, so why can't we give it a go?"
"Because we're Time Lords," Romana said, "not insects."
"It's an important part of the human experience!"
"Then find a human to try it with."
"I did," he said, and twiddled a knob sulkily. "She said I was doing it all wrong. Come on, where's your intellectual curiosity?"
Romana wasn't convinced that Great Romantic Tropes of Our Time was the best text to use to investigate human mating rituals, but what the hell. It all seemed reasonably harmless.
Running along the (blue) beach at (green) sunset while holding hands was quite nice, although they probably weren't supposed to be being chased by giant slugs when it happened. Fortunately the slugs were slow and it turned out the sand was lethal to them, so at least she and the Doctor escaped un-slimed.
The first kiss bore considerable scrutiny. Eventually they agreed on a verdict of 'all right, but slimy', and spent a happy week researching the possibility that human lips released endorphins under pressure, which was much more enjoyable than the kissing.
Neither of them fancied oysters and chocolate in the same meal, but they were determined, so Romana broke the ingredients down into their component molecules and made them into a nice sensible soup.
The Doctor said it was the best reconstituted food he'd ever tasted, and accidentally set his scarf on fire with the candle.
Cuddling was very pleasant, but they both knew that already.
Romana prodded curiously at the large bouquet. "And what do I do with them now that you've given them to me?"
"I don't know." The Doctor shrugged. "Experiment on them?"
She took cuttings, got them to grow under five types of sunlight, discovered three new uses for Terran chlorophyll while she was at it, and wrote a paper.
They'd done Paris already.
Getting caught in the rain was harder than it sounded, especially when the TARDIS landed them in an arctic climate. Still, snow was on the list, too, so they dug in, made forts and pelted one another until they got too cold to carry on, which took about two days.
It was messy and damp and childish and fun and glorious, but it didn't make her want to mate with the Doctor as much as it made her want to get a snowball down the back of his scarf.
The Doctor squinted up at the clouds scudding across the sky. "Look! A cirrus fibratus!"
"There's a cirrus uncinus over there," Romana said, and sighed. "These still aren't rain clouds."
"Maybe not, but at least we can tick cloud-watching off the list."
"Yes. You know, it's funny, but I've not met many humans who knew their meteorology that well..."
Watching the Doctor sleep was far from thrilling. She caught him napping in the garden and took some notes, then wondered what he was dreaming about — apparently an important part of this ritual.
This was silly, she decided. She could easily find out, and doing so would be much more enjoyable and sociable than just sitting here watching. She laid down next to him, closed her eyes, and they shared a wonderful dream about custard threatening UNIT.
The Dryneans hadn't had rain in three generations, thanks to a hydrophobic overlord with a primitive meteorological control device. The Doctor was gratified to learn that the overlord and all his minions melted when dampened, and had the machine producing a downpour in minutes.
"Now what?" Romana yelled over the rolling thunder.
He didn't know. So they stood there for a while, then went back to the TARDIS to dry off.
There were no hearths in the TARDIS, so they built a roaring campfire in an empty room, found a decent vintage in the wine cellar, and toasted jelly babies.
Romana gazed thoughtfully at her pink sweet as it melted in the flames. "I take it that means we're in love now."
"Yes. We've done everything on the list."
"It's a lot of fuss for something so simple," she said. "I know it's not obvious for them, but can't they just tell one another?"
"Oh, they do." The Doctor tugged a melted orange mess from one of the prongs of his toasting fork and popped it into his mouth. "But, you know, they're not telepathic. They have to keep proving it."
"I see." Her jelly baby dropped off the fork and landed in the fire with a pop and a sizzle. Romana sighed. "So what do they do next?"
"Do you know, I've never had a satisfactory answer to that. It seems to be rather private."
"Oh." That was a shame, she thought. It would have been interesting to see this experiment to its proper conclusion.
"So I thought maybe we could cuddle and do some maths."
She beamed at him. "That would be delightful."
The Doctor grinned back. "Well, we are Time Lords."