For my daughter's fourth birthday, we had a wizard of oz themed birthday party. She dressed up like Dorothy, including the ruby slippers.  The party took place in a large family room where the movie soundtrack played. I made the Emerald City with green poster board and LOTS of glitter. A pair of stuffed tube socks with black stripes drawn on them were curled up and stuffed under the couch to represent the witch.  We hung rainbow colored crepe paper all over the room. I found pictures in a Wizard of Oz book and made huge copies of the pictures.  Some pictures I hung around the room and others were glued to foam board and stood up.  I made the badge of courage, the ticking heart, and an axe out of poster board and hung them up around the room.  To recreate the finding of the scarecrow, I brought large pieces of wooden fencing in the house and a cube of straw and hung a picture of the scarecrow with a sign that read "If I only had a brain!"  We made a 60ft. long yellow brick road out of paper with bricks drawn on it.  Also, we bought 3 dozen balloons- 1 dozen was hung all around the room, while the left over 2 dozen were strung together in a rainbow shape (over the rainbow).  We ate rainbow candy (which was guaranteed to produce feelings of "intelligence, courage and love") and drank melted witch punch (green colored). The cake had a airbrushed rainbow on it and an edible picture of the four characters and toto. Everyone loved the decorations, and my daughter said it was her favorite party yet!