Whereas Artoo had never really had to share Luke before. Not since Yavin. Whoever else came and went and was there or had other missions, Artoo was always attached to Luke and his X-Wing.

"You're just going to have to learn to share," Luke pointed out. "It's not like you're being replaced, but Cal's special and he's not going anywhere, okay? Not unless he wants to." His hand rubs over the dome again. "I don't get jealous of Threepio, do I?"

Artoo's sound suggested that no, Luke didn't do that.