Unfortunately, observing Jareth when he's observing someone himself doesn't lead to a great deal of information; the Goblin King, however, has an unmistakeably haughty air about him and an almost permanent look of mild disinterest.

This doesn't change when the massive creature lands, even if the dragon is a curiosity.

In response to the dragon's question, Jareth makes a show of looking to his right, his left, and then back to the dragon. "I certainly don't see him now."