A non sequitur interjection meant to imply ADD (attention deficit disorder). So called because it seems the stereotypical thing a young girl might scream when having her attention distracted by ponies. Common in many online forums.
Wow, I just read in the Washington Post about a secret US plan to attack China. Now this would obviously be a terrible--OMG! Ponies!!!
by SkidMarkyMark June 01, 2006
an involuntary exclamation when confronted by extreme awesomeness or cuteness
"I logged on and and saw the pics of your new l33t rig and thought "omg ponies!"
by Staniel Cabio July 13, 2006