It is a little like they're surprised that they're still there and visible every new time that they're addressed. It's like they never expect to be taking part in whatever's happening around them. Robin suddenly including them in the meal is treated like a delightful novelty.

Phalanx smiles and reaches for the offered food (and not the plate itself) when Robin holds it out. And the extra clarification is appreciated.

"I don't know," the ghosts answer cheerily. Let's find out!