Yarr! is like saying yeah! It can convey a sense of loss, a feeling of resination, and can even confirm agreement, but more appropriately it's just yeah.
Yarp Yarp (or Specimen Yarp) is an abomination created from a freak incident involving a spider, a hammer, a basketball and a bathtub. Formerly known as Kenny Hotz, this creature is an untamed beast that can only be controlled by being fed used tampons.