It's different for each:
Merry Piper loves tiny, squeaky tennis balls and likes to hoard and arrange them, e.g. a little pile behind Daddy, three more by her dinner dish, etc. She will share them, though, with our cat as they are frequent playmates.
Keegan Riley has no use for a ball. His favorite toy of all time is his "crazy chicken" that has to be replaced so often we always keep a backup supply.
They agreed to pose with their Wonderful Things:
