Y stands for preved
(An Internet term and the biggest ever flashmob in the history of russian Internet community) because of its similarity to the figure ("medved") from the well known picture, originally drawn by John Lurie. The drawing was altered in a minor way by replacing the word "surprise!" with the word "preved!" (by its russian spelling, of course) Actually, it was Medved (a bear) who said "preved" to a couple of people having sex in the wood.