Just a drabble that came to me and I couldn't help but jot it down. Hope you enjoy.
"How do you expect her to take a flirt like you seriously? She'll never believe your feelings are genuine if you go around flirting with everybody," Marinette gave Chat Noir a stern look and poked a finger in his chest.
"What?" the cat hero yelped, indignant. "I only flirt with her, no one else!"
"Oh-ho, really?" the bluenette shot him a narrow eyed stare before an idea came to her and the corner of her mouth flipped up into a smirk. A smirk which looked a lot like the one he usually wore.
She turned to face away from him and shook out her limbs, getting in to character. Chat looked on perplexed, curious as to what she was about to do. He didn't have to wait long.
Marinette turned around and dropped to one knee.
"I haven't introduced myself, I'm Chat Noir," she proclaimed, deepening her voice in a poor imitation of his and grabbing his hand to place a kiss on the back before standing back up.
"I don't sound like that," Chat grumbled. Marinette just raised an eyebrow at him before continuing.
"That birthday boy date of yours is bad news," Marinette turned around and starting posturing and flexing. "But don't worry, you'll be safe with me." She advanced towards him and Chat Noir backed up at the predatory look in her eyes before his back hit the wall. She leaned towards him, resting one hand on the wall next to his head. He gulped, his Adam's apple bobbing in his throat.
"Ladybug's busy tonight so... You get to be my Ladybug," the smirk on Marinette's face was getting bigger. Chat was starting to sweat, nervous at her nearness and the dawning realisation that she was right. This did seem a lot like flirting. He hadn't even realised that he had been doing it. Chat Noir was re-evaluating everything he thought he knew about himself and it was making him panic. What did all this mean?
"Just get that drawing pencil away from him, Princess. I'll take care of the rest," Marinette finished, straightening up and rolling her eyes as she gave him a two-finger salute.
"I... I... you, but... um..." Chat Noir desperately looked around trying in vain to come up with some argument against her. "Well, what about you? You can't tell me that you weren't fan-girling over me. You were so excited, I couldn't let down a fan. I have a reputation to uphold."
Marinette's mouth popped open to form an 'o'. She tried desperately to dispute his claims but could think of nothing that wouldn't give away that she was Ladybug. A faint blush crossed her cheeks and she mouthed mutely for a minute, trying to form words. She wanted to wipe the look of glee off his face but couldn't.
"That," she stated in an annoyed tone, "is neither here nor there. I was just proving you flirt with other people as well. So there," she knew it was childish but she stuck her tongue out at him.
Chat flushed red and spluttered nonsensically. He finally managed to string together some words that almost made sense.
"I... to go... must," he stuttered, backing up to the window and hopping on to the sill. "See you later!" he called and with that he was gone. Marinette wore her self-satisfied grin for the rest of the day.
I know that in the English Dub he calls her 'little lady' but I prefer 'Princess'. I hope you enjoyed this.