Disclaimer: I do not Death Note or any of its associated characters or fictional locations.
Once upon a time there was a boy named L.
Nobody knew why they called him L, he was just L.
He was weird that way.
He walked funny, and looked like a panda.
Nobody knew why he walked funny and walked like a panda.
He was also weird in that way.
Then one day while young L was walking funny found an empty glass jar on the ground. L found this strange due to the fact that the jar had been full earlier on, and yet it was empty so soon.
Much to L's surprise he quickly found more empty jars like a trail of breadcrumbs, except less tasty.
L decided to follow these jar's to their source, because he had nothing else to do and if he hung around too long Rodger might find him and make him take a bath.
So L followed the Jar trail, winding all around the orphanage, over the hill, through the basement, beside Watari's secret collection of adult magazine's, until, until finally he reached the kitchen door.
From within the door young L could hear a lot of strange noises, like a sort of sucking and moaning and gasping. Curious as to what could be causing these sounds L opened the door.
He was unprepared for the sight that met him. Before him was the kitchen, however it was not the pristine white and chrome room that he remembered, the room was covered in empty jars and flecks of Jam, in the middle of the room there was BB sitting on a stool, spooning out big globs of Jam for the jar in his hand.
"BB, what are you doing?" Asked the confused L.
"I'm eating all the Jam, what does it look smararse-"
"Oh ye gods that's where all the Jam has been going!" Proclaimed Rodger, who had been secretly stalking L so that he could kidnap him and make him take his first bath in over a month. "Well done L, you managed to solve the mystery! Here, have some money as reward," Rodger gave young L a few pounds.
"... What's this?"
"..Ah, it's called money you buy things with it, like food or clothes or-"
"Like candy?"
Rodger rubbed his temples. "Yes like candy."
"And you gave me money for finding out who kept eating all the Jam?"
"Correct."
"So if I solve mysteries I get money?"
"Yes L, yes you do," sighed Rodger.
"And more money means more candy?"
"Yes, L, more money means more candy-"
L grinned, revealing surprisingly white teeth for a boy with such bad eating habits. "I know what I want to be when I grow up Rodger!"
And thus L embarked up the journey that would lead to him becoming the world's greatest detective and having all the candy he could eat, having learned that while crime may not pay catching criminals does.
As for why he would later contribute to the scarring of one of his successors many years later by having an orgy with his father figure and his friend?
He was just weird that way.