A community of terraced houses along a street could agree to have all their garden fences mechanised, so at the push of a button they can lower them to connect each lawn (or just a few) and create one large 'pop-up park'.
It could provide a safe and convienient place away from the road for children
to play and for neighbourhood activities to take place e.g. a game of football, a barbeque, a street party (without closing the road).
An optional addition to enhance the 'pop-up' theme would be to have 2D designs arise in some of the fence's places, such as trees, hurdles, skyscrapers, aliens... anything! It could also be designed as a whack-a-mole game, or a pop-up storybook for children to walk through and explore all the giant flaps and artworks, telling a story from one end of the neighbourhood to the other.