First, Lucy's cover! Or lack thereof!

"So, are we going to just tell the others about me being your genie?" Lucy asked Natsu as she nuzzled her head into his chest.

"I'm not sure about that... other than just pretending nothing is different, I don't se an alternative," he mused.

"Oh, I might actually have an idea about that, Master!" Lucy remarked, clapping her hands together in glee. "What if I was always your genie?"

"Um, what?" Natsu asked with a blink. "How would that even work?"

"A simple wish to alter the memories of everyone just a little bit! Enough to make them think I was always some cosmic being in your service when you found me!" Lucy grinned. "I wouldn't even need to change their memories of my involvement of our Quests! Just change their knowledge of my nature!"

"And would this affect your relationship with your Celestial Spirits at all?" Natsu inquired.

"Hmm, well, it shouldn't, even if the wish affects them, I shouldn't have any problems being able to Summon them regardless!" Lucy assured him. "Also, there are some pretty lovely ladies among the Spirits... maybe I can allow you to have a sexual relationship with them as well?" she purred in mischievous delight.

He blushed at the thought. "Hmmm... that actually doesn't sound that bad... and if people already know you're a sexual being, it won't seem out of nowhere if we suddenly start making offers to improve people's sex lives... we can also say that I waited before going all the way with you because I wanted to get to know you first, I guess?" he suggested thoughtfully. A rare sight from him, he tended to be a hothead, though Lucy knew he wasn't a complete moron. He just needed a nudge to think things through from time to time. "...you know what? Let's go that route!" he decided.

"Yay, no need to hide what I am!" she cheered, floating up off the bed and doing an excited loop de loop.

"Lucy, I wish that as far as the world was concerned, you were always a unique sort of spirit bound to me, and that no one can take the lamp from me without my permission so as to ensure we don't have to hide our relationship from anyone," Natsu wished.

"Your wish is my command!" she chimed, snapping her fingers, and sending out a massive pulse of magic that would spread across the planet. This made her woozy briefly, as it was a large scale wish, but she recovered and grinned.

(Credit goes to SomethingOdd for this idea. It wasn't my original plan, but the idea of exploring a dynamic where everyone just knows Lucy is Natsu's genie **** automatically is something I couldn't resist.)