Here’s something I found and just had to share. While not exactly an outdoor activity, this awesome prank could send your family running outside! There also may be some screaming, so get those ear plugs out.
Just create a continuous graphic by taking two photos of your face from the front and the side. Then merge them in Photoshop (a free open source alternative to Photoshop is GIMP) as shown here:
Take a look at the full project tutorial from mikeasaurus on Instructables.