Moths
Light's seen a lot of strange things in his life. That included a notebook that could kill people, Shinigami, and that obsessive man who worships him like God(it was flattering, but...). Therefore, one would have deduced that one this one particular afternoon, when L came into the room with a jar full of moths, Light shouldn't really have been surprised. He shouldn't have been surprised either when L promptly twisted the jar open and set the moths loose.
Immediately, the insects swarmed around Light. The brunet figured that it wouldn't be the best time to yell at the raven-haired detective right then; one of the moths had nearly made its way into his mouth.
When the moths finally seemed to lose interest, they began to fly out the open window. Eventually, only a few remained, and Light was able to talk. "Ryuuzaki," he began, but stopped when he saw a hint of a smile on L's lips.
"So it's true," the detective said around his thumb. "Moths are attracted to Light." He turned and walked past the doorway. "How intriguing," he mused, shook his head, and disappeared down the hall. The door managed to slide shut by itself.
And so the piece of wood was the only thing in the way when Light screamed, "WHAT THE HELL IS SO INTRIGUING ABOUT MY BEING SWARMED BY MOTHS?"
Seriously, L, what is? :\ Erm...fail attempt at writing Light and L? :D