Ok. I'm on like frigging episode 4 of Death Note, but why does L always have his thumb in his mouth?

Maybe it's a personality quirk?

He's a baby~

Because he's L. *shot*

My friend tell me he had disorders.

Some people like to do that sometimes...*inserts thumb in mouth*

Helps hi think with that great brain he has .3.

From what I can tell, it either helps him think или it's a symptom of his autism. Autistic people do this thing called stimming, where they make a repetitive motion (like spinning или flapping their hands) или do something strange (like sucking their thumb) and it keeps their anxiety down.

L's quirky, he's not used to being around people. Oh, and he's biting his thumbnail, which is a habit i've picked up on.

Yea, all of L's quirks are best explained in the book L Change The World.

i'm sorry i don't know i think bcoz animators made him but it looks cool

lol, what's deathnote?
i mean i hear it all the time since i joined fanpop, but i have no idea what it is!

Because he's L desu.

All of his smartness comes from his thumb so when he bites it, it all goes to his head and makes him be smarticle.

I think it's probably because in episode 10, he says "it helps me think" или maybe it was another episode. He also has bad posture and wasn't cared for as a child, so it could be that his so called "parents" never told him to break the habit when he was a child. That's just coming from little ol' me, an animator. <3