I doubt that aliens would be in sewers, unless they have sewer-ships.
DID A UFO PLAY MY QUEEN TO D1 ON MOVE 7
maybe it was this guy
http://www.chess.com/members/view/shadow-psyche
in his profile it is stated
- Member Since: Sep 5, 2011
- Last Login: May 1, 2013
- Profile Views: 524
- Points: 43
Birthday: Jan 1, 1901
Occupation: extraterrestrian
Off spring off the marooned ones,
Also he only belongs to one group and it is the Bobby Fischer Group



Maybe it was a CHUD!