The phrase pegged in this sense means figured out or summed up, which is why the clip travels as a reaction sound rather than a scene people quote from a known film or show. No clear original source is attached to this upload, so its life is in edits, soundboards and short form videos where creators reuse short voice lines as instant commentary. It stays useful because the meaning is clear without context, fitting arguments, gaming moments, dating stories and any clip where someone thinks they fooled everyone else.