Here's just a quick run down with pictures from Secundus' 5th birthday party. I don't decorate and generally like to keep things simple:
Rainbow Fruit Salad. Strawberries, clementines, pineapple, pear, grapes.
Cupcakes with unicorn horns on top. I covered sugar cones in frosting, rolled them in colored sugar, and then wrapped them with Twizzler Pull-and-peels.
Inside the goody bags: Ring Pop, chocolate-peanut butter Bugles (unicorn horns!) and a playdough kit.
Hotdog Unicorn Horns. I wrapped hotdogs in strips of canned pizza dough and cooked them on a greased cookie sheet for a little longer than the package recommended.
Party Games: Pin the horn on the unicorn and a relay race. For the race, they had to gallop to one end of the room to pick up a rainbow tale strip and then gallop back to tape it to the unicorn picture.
Unicorn horns party hats. Simply made from construction paper with gold glitter swirls and tied on with yarn.