A popular theme that works well for either a boy or a girl is a clown or other circus_related cake. They are usually very bright and colorful, which makes for instant attraction and a great focal point for a party table.
Sports Cakes: Your active girl or boy will jump for a sports themed cake. Some easy birthday cake ideas are decorating round cakes to resemble baseballs, soccer balls, or basketballs. Sporty girls and boys will also love a cake that resembles their favorite sports field, which is easy to make with a rectangular sheet cake. You can even add a net, goal, or hoop, as well as plastic figurines resembling spectators and sports players!