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!!!
ayon kay SkidMarkyMark ika-01 ng Hunyo, 2006
1 more definition
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!"
ayon kay Staniel Cabio ika-13 ng Hulyo, 2006