Shiraneyo

  ∧ ∧     ┌─────────────
  ( ´ー`)   < I don't know...
   \ <     └───/|────────
    \.\______//
      \       /
       ∪∪ ̄∪∪

Shiraneyo (シラネーヨ) is an odd creature. Its name means "I don't know" or "I don't care", and it responds to every question with this phrase. Is it a dinosaur? I don't know. It has a mole in its neck.

It doesn't show up very often, as 2ch users find it hard to use.

Derivatives:

Shiranaiwa

  ∧∞∧   ┌───────
  (*‘ー‘)   < I don't know...
   \ <     └───/|───
    \.\______//
      \       /
       ∪∪ ̄∪∪

Shiranaiwa (シラナイワ) is a female version of Shiraneyo, usually portrayed as Shiraneyo's girlfriend.

Chiraneyo

        ___
   ∧ ∧ < i dunno
   (´ー`)_/| ̄ ̄ ̄
    UU UU

Chiraneyo (チラネーヨ) is a baby version of Shiraneyo.

Kuukiyometeneyo

〇          )\ it's so hot...
   O     <⌒ヽ ヽ  / ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄
     o   ( ´ー`) < I can't read the air...
     ┗─^V(   丿V^\_______________
          ヽ (
            )  )
           ノ ノ
           レ′

Kuukiyometeneyo (空気読めてネーヨ) is a gaseous character derived from Shiraneyo. He mostly tells people to read the air in situations, which is what his name means.

________.  |  ・・・"roum"?
|||          | \____ __
|||          |  )\       ∨
|||    ROOM   <⌒ヽ ヽ
|||         \ ( ´ー`)    ∧∧
|||_________V(   丿V^  ●Д゚,,)
|,,|          |,,| ヽ (      と  ,)
              ノ )     |  |~
            ∧          .し`J,,.
 ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄  ̄ ̄ ̄\
 Read the fucking room.

Shirane no Orochi

 ./ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄ ̄\
 |    シラネノオロチダーヨ    |
 \_  __   ___ ___   __ __/
   ∨  ∨∨ ∨ ∨∨   ∨
          ∧ ∧
          (´ー`)
        ∧ ∧  ∧ ∧
       ( ´ー`) (´ー` )
      ∧ ∧. |  | ∧ ∧
 ∧ ∧ ( ´ー`) | | (´ー` ) ∧ ∧
 ( ´ー`) \ <  | |   > / (´ー` )
  \ <___\.\∨/./ ____> /
    \__ ̄      ̄.__/
       ./  |l|  ヽ
       | .|__.∧l∧__| .|
       .>| (´ー`) |<
       ¨¨       ¨¨

Shirane no Orochi (シラネノオロチダーヨ) is a derivative of Shiraneyo based off of the legendary Japanese dragon Yamata no Orochi (specifically the version of it from Dragon Quest 3).

VIPsaurus

  ∧M∧     ┌─────────
  ( ´ー`)    < Hello, I am VIPsaurus ask me anything.
   \ <      └──────────
    \.\                       /|
      \.\                     //
        \.\                    //
          \.\∧∧∧∧∧∧∧∧∧∧//
            \               /
             ∪∪ ̄ ̄ ̄ ̄ ̄ ̄∪∪

VIPsaurus is a derivative of Shiraneyo that only shows up on English-speaking textboards. It answers people's questions and then shouts "NEXT!" for more.

  ∧ ∧   ┌──────────────
  ( ´ー`) < Say hello to the new family!
    \ \ └──────────────
     \ \ ∧∧           ∧∞∧
  ∧ ∧ ∧ ∧(´ー`)      ∧∧ (*‘ー‘)∧ ∧
  ( ´ー`)´ー`)⊂ヽ \/| ∧∧(´ー`)  \ < (‘ー‘*)      /|
  |  つ|  つ\ ⊂_,ノ(´ー`)∪∪ ̄ ̄ \⊂ヽ \/|____//
 ∠ 丿∠/|ノ ∧∧_ ̄ ∪∪     ∧∧\⊂/| ノ_   /
  ∪∪⊂^⌒⊃´ー`)⊃ ̄ ̄ ̄∪∪⊂(‘ー‘*⊂⌒^⊃ ∪∪

Sources: