With the addition of Snappy Smurf to the island there are now three Smurflings available (Snappy, Slouchy and Sassette). If the houses have been placed next to one another, the Smurflings will perform a dance once a day in front of their houses. Once they are ready, there will be a sign above Snappy’s mushroom house. The dance awards XP every 24 hours. There are certain items available, which, if placed near to the Smurfling’s Huts will increase the XP of the dance.
Those items are a train (10 extra XP per train) and a toy chest (15 extra XP per chest). To see if they are placed close enough to be affected, tapping on one of the mushroom houses of the Smurflings will turn all items green that are in range for the extra XP bonus.