For the last few weeks, we've been saying 'FISH' to grandson #1 and then making fish mouths (open, close, open, close, open, close, like a goldfish) and he very quickly started looking at each person in turn as if he was making sure they did it.
Yesterday, I said 'FISH' and after he'd looked around at us all he then made a fish mouth as well for the first time. It's almost as good as when he started waving back when you wave at him a couple of weeks ago.
Proper happy at that. He seems to enjoy it as well.