A/N: Oh, I don't know. I just thought about this and decided to try and write a fic about it. I don't own Doctor Who or Katy Perry. This is taking place before the Doctor knows who River is, definitely.
Extra-Terrestrial
The Doctor and River were bickering over which lever was the most useful to pull in the case of extra gravity when orbiting an ultra dense planet. River waved to the Ponds as they entered the main control room for the morning, but the Doctor was still talking at her ear as she pulled a lever right then down.
"Doctor?" Amy strode onto the console platform with a skip in her step. "Has the TARDIS got a CD player?"
The Doctor sighed and shook his head at the woman with the curly hair. He raised an eyebrow at Amy, abandoning his attempt at conversation with River. "Amy, this ship can travel us to anywhere in space and time. We can literally go to all ends of the universe. Do you honestly think it would have a music player from twenty-first century earth?"
"Sorry," Amy rolled her eyes. "It was just a question."
River strode around the TARDIS, a smile on her face. "No CD player, but it has an iPod jack. What did you want to listen to?"
Amy gave River a mischievous smile. The Doctor frowned, hating it when the women shared a secret. It was almost always about him. He had to remember to keep his female companions apart.
"Remember that song I showed you? I thought it might be fun to play it for the Doctor." Amy pulled an iPod from her back pocket, waving it with one hand.
"Does it matter that I'm uncomfortable with this?" Rory asked, waving his hand in the air, reminding his wife that he was there. "Yeah, didn't think so," he answered his own question while she and River continued whispering to one another.
River took the iPod and walked to a location on the console particularly laden with wires.
"River, the TARDIS hasn't an iPod jack. Honestly." The Doctor was watching the woman rifle through his wires, picking ones here and there.
"I can reroute the alarm system to play whatever comes over the audio stream. This wire and this wire together, plus this one for an amplitude boost? That'd work, yeah?" She showed him her makeshift jack, an annoyingly confident smirk on her face.
"I'm sure that the earth technology has some sort of security against this, and anyway, what if I need the alarms?" the Doctor mumbled, avoiding her question.
"Sweetie, sonic me?" River held out the iPod. "A short alpha blast should wipe the security system?" The Doctor begrudgingly obliged, sending the sonic signal at the music player, as River continued talking. "And anyway, you have the alarms turned off."
She connected the iPod. "Amy, I think we should serenade him." She met the redhead's eyes, their playful stares identical.
Amy grabbed River's hand and they turned toward the Doctor together.
The Doctor tilted his head, backing away instinctively as the TARDIS began to beat with rhythm and his two beautiful women advanced on him.
"Just so you know, I did not approve of this," Rory told the Doctor, his eyes apologetic.
"Then control your wife!" The Doctor's voice was obviously alarmed.
"Sweetie, don't be so patriarchal!" River grinned at him, and Amy pushed her forward.
"Your part first, River," Amy said, laughing.
"You're so hypnotizing," River sang, dragging her finger across his chest.
He jumped backwards, his eyes widening.
"Could you be the devil?" She raised her eyebrows suggestively as she pulled the lapels of his tweed toward her, so that their bodies were flush. "Could you be an angel?" She let him go, and he stumbled into the railing of the console.
"Your touch magnetizing. Feels like I am floating, leaves my body glowing." River sang the words softly against the console, her voice barely reaching the Doctor, who swallowed nervously.
Then Amy grabbed his hand, pulling his gaze from River's. "They say be afraid. You're not like the others," the redhead took over singing. "Futuristic lover." She twirled the Doctor around, forcing him to make an awkward pirouette.
"Honestly, what the hell is this?" the Doctor yelped as Amy pirouetted and serenaded him. "Why would you sing this song to me?"
"Different DNA. They don't understand you." Amy smiled at him as he cocked an eyebrow at the lyrics.
"You're from a whole other world," River's voice intoned from the other side of the console.
The Doctor laughed as Amy pushed him to River, who grabbed his waist and held his hand like they were waltzing, and he was the girl.
"A different dimension."
"Well not precisely," he murmured, moving her hand to his shoulder and placing his hand on her waist so that he would be the guy in the waltz.
"You open my eyes." River's eyes were amused, but she sang close to his face, and he was mesmerized by her smirk and her edge of sincerity. "And I'm ready to go, lead me into the light."
Then River let him go, and she and Amy sang the chorus together, laughing around him, and Rory crossing his arms with insecurity.
"Kiss me, k-k-kiss me. Infect me with your love, and fill me with your poison!"
"I am not poisonous! This is a terribly rude song!" He protested, but he had a smile on his face.
"Take me, t-t-take me! Wanna be your victim, Ready for abduction!"
"Now that's just uncreative. AND very stereotypical. I don't abduct people, honestly," he scoffed.
"I beg to differ," Rory murmured.
"Boy, you're an alien. Your touch so foreign. It's supernatural. Extra-terrestrial."
The Doctor just laughed as the girls yelled/sang the lyrics at him and made him dance, and he could not help but dance too. He loved to dance.
"You're so supersonic," River sang in his ear, pulling him close and stealing his sonic screwdriver from his front pocket. He tried to grab it but she held it so that he had to lean over her, and he did not realize how close he was until she was continuing the song so closely to his neck that he shivered. "Wanna feel your powers. Stun me with your laser."
"That's inappropriate, River," he wiggled his eyebrows with a flirtatious grin as he pulled himself off of her.
"Your kiss is cosmic."
"Well, I've heard that I'm pretty good—" he flipped his hair.
River let the lyrics continue without her, taking a step toward the Doctor and saying instead, "Sweetie, that line was definitely about me."
"The song definitely says that the alien has the supersonic kissing abilities," he countered.
"Who said I'm not an alien?" she asked, smirking.
"What—but…" His eyes widened.
She placed a finger over his lips and pulled his ridiculous face down to her and whispered, "Spoilers."
"Quit being the boringers, guys!" Amy tapped River's shoulder.
River smiled at the Doctor, pulling him from his thoughts about her, and forcing him to dance to their ridiculous song.
Rory even joined, serenading their alien and how supersonic he was. The Doctor pretended to be disgruntled, but he even was singing, although he found the part with vibration a bit disconcerting. "How do you walk on a wavelength? And why would an alien vibrate?" He asked, and then shrugged. "Well I guess if you're one of the vibrating Sannesh from Alpha Nine Sigma, you vibrate fairly frequently, especially with all of those wars—"
"Doctor! Shut up, Sweetie! Stop thinking and just sing!"
He laughed and twirled with River for the ending cords of the song.
When the song ended, "Peacock" started with "I wanna see your peacock" the Doctor coughed uncomfortably.
"Don't worry, Doctor, this song isn't on the agenda," Amy assured.
"Not yet anyway," River added, grinning at the Doctor. The Timelord flushed.
"INAPPROPRIATE!"