Omgyg2bk is text speak for Oh my gosh you've got to be kidding.
Example:

Chuck: Seema have you seen the news? The worlds been took over by aliens who plan to kill half off the human race and keep the rest for slavery.

Seema: OMGYG2BK!

Chuck: Just kidding you fool.

Seema: Whatever *walks off annoyed*
by Tallulah DaSouza June 12, 2010
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