Ideas for a Ben 10 or alien party theme

Pizza with green and yellow toppings like green and yellow peppers, green olives, pineapple.

Bake cupcakes and let the kids decorate them as their own Omnitrix green frosting and candies to create the dial.

Green and yellow goody bags filled with Pop Rocks candies, green slime, green plastic watches (dime storm to look like the Omnitrix), andor any other Alien items you can think of.