Some friends of ours bought a house in a very swanky neighborhood. We snuck over at night and placed plastic lawn ornaments all over their yard (including pink flamingos).
Best part was that our friends couldn't see the "decorations" from their window. They couldn't figure out why all their new neighbors slowed down as they passed the house!!
A bunch of us actually did the flamingo thing at a friend's house in a posh neighborhood, too, while he was in Europe. Dozens on pink flamingos grazed all over his lawn for a week before he got home!