He--well, it's nearly a giggle, but doesn't quite cross the line over from chuckle--laughs a little and scritches it more, idly wondering whether and when Joker is not-planning to grab his wrist and yank him down from the tree.
"You," Xel informs sock-Xel solemnly, "are definitely unique." He stretches, and curls up like a monkey's tail, ending sprawled on his stomach along his branch. "What are the things that don't go boom?" he asks curiously.