For my son Brandon's fourth birthday we had a race car theme.  For invitations I bought white cardstock which I cut in half and then cut out a winding road out of black construction paper and glued it on.  I used a paint pen to do the white dotted line of the road. Then I hot glued a hot wheels car on the "road".  The invitation had a poem that I made up; Vroommmm, Race on over and don't be late, Brandon is turning four, we have to celebrate! For decorations we made a balloon arch out of black and white balloons and had checkered flags everywhere. We rented a inflatable jump that had a race car on top, just to give the kids something to do when we were not doing an activity.  For activities, I made several "stations" that the kids could do or make something.  Station #1, the DMV, I bought and Izone camera that is instamatic. The film that comes out is quarter size. I took each childs photos and put it on licenses that I had pre-made with there d.o.b, name, ect. Then I used those photo lamination kits and made license for the kids. Next station was build your own race car from candy.  Use a pack of bubble gum for the body, round red/white christmas candies for the four wheels, and miniture hersheys candy bars for the spoiler.  The kids loved these. THe third station was make your own stoplight goody bad. Made out of lunch bags and red, green, and yellow construction paper circles I had cut out before hand. We used these for the goodies that fell out of the race car pinata.  I also set up race car tracks (hotwheels) around the yard. Since this party was in the latter part of the afternoon, instead of serving lunch I set up an icecream sundae buffet with every imaginable topping and the kids had to "race on over" and make their sundae.  For the birthday cake I ordered a 4-d racecar cake kit from racecakes.com. The kids received racing helmets, and hotwheel cars and candy for goody bags.  It was a great day for all, and I got a lot of compliments!!!!