Floating Presents
From Wild World Wiki
Floating Presents are often found in AC:WW. They are essentially presents tied to a balloon, floating in the sky (shown on the top screen of the DS when outside and not in menu mode). They can be shot down using the slingshot. Make sure you are accurate, as a miss may cause you to lose the balloon (either by letting it past or by shooting it down into the water).
Floating Presents will only appear at certain times- times that end with 4 minutes (i.e. the time would be in HH:M4 format). It also seems that they will only appear during daylight hours.
When unwrapped (as you would unwrap a present attatched to a letter), the present will reveal an item, most often a piece of furniture, although other items have been reported.