Assō (あっそー), aka Mr Quietly

　 　　　　 ／￣￣￣￣￣
　冫、 　＜　　o rly
　` 　　　　＼＿＿＿＿＿

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|⌒彡
|冫、）
|` ／
| /
|/
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| 　hush
|）彡
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He will just sometimes sneak up in a thread, peek out and give a tiny remark in the above fashion, only to instantly vanish as quickly and quietly as he appeared.
http://members.at.infoseek.co.jp/maruheso/aadic/aa.html#asso