Yes, it's a new twist on the classic Wizard of Oz story. Batman gets involved and of course saves the day.
And I know that's a tiger and not a cowardly lion... call it artistic license. Two flying monkey outfits and a Dorothy dress where about my limit. My sanity levels were already balancing on a fine line after an entire morning looking for ruby slippers in the shops and the Tiger was extremely happy to be a tiger and not a cowardly lion (and we already had that in our dressing up box... bonus!).
Batman? Well, we may well have needed more than his super powers to save this particular Wizard of Oz show (No songs from the movie whatsoever AND Dorothy wore silver shoes ... can you believe it?!!). I think his in ability to save the show was why Batman is looking so particularly serious in the below shot.
It could of course be extreme concern over his Aunty Sarah's wearing of a flying monkey hat and wings whilst having a photo taken with a scarecrow and Dorothy. Or perhaps he was little more worried about his Nanna...
Whatever it was, these super heros don't have it easy you know.