Natsu doesn't have a superior knowledge of the English language, and he's quite well aware of it. And there's no harm in having a little fun exploiting that fact.

"Hey, Lucy?"

"What's up, Natsu?"

"Think ya could help me out? My reading isn't all that good, and I thought maybe ya could answer some questions!"

"Sure thing! What do you need help with?"

"Well, for starters, how many letters are there in the alphabet?"

"Twenty-six. You mean you don't know even that much?!"

"No, I always thought there were twenty-one!"

"No, there's definitely twenty-six."

"Oh..." Natsu thought a moment, then grinned. Lucy wasn't sure she liked the grin. "I guess I left out U, R, A..."

"What...?"

The smile grew. "Oh! Q, T!"

Lucy's face turned an alarming shade of pink. Almost red, in fact. "N-Natsu!"

Natsu shrugged. "What? It's the truth!"

Then turned to talk to a giggling Mirajane.

Erza laughed from her seat next to Lucy's table. Lucy gave her an almost pained expression. "Was he faking it?"

An almost deadly, rather sadistic (Erza-esque) smile covered her face. "Yes, indeed. I taught him everything he needed to know when we were kids." The smile grew. "And what I couldn't teach him, I beat into him." She stood, presumably to get more strawberry cake.

Lucy sighed, facepalming. She began to wonder why Natsu had even bothered with their conversation...

"What? It's the truth!"

She smiled, hoping to herself that it meant what she thought it did.