For the cupcake, all you have to do is get a box of yellow cake mix and follow the directions, replacing the cup of water with 12oz of Mountain Dew. I used Diet Mountain Dew, because that's what we always keep around in our house. My family is kind of obsessed with it.
For the frosting, I just followed the recipe from The Geeky Hostess, using a few drops of green and yellow food dye (the yellow makes it brighter). Then I took a large Ziploc bag, cut the corner, put a frosting tip inside it, and then added the frosting into the bag to frost the cupcakes with (just don't put a rubber band around the tip like I originally did).
They actually taste pretty good and everyone in my family enjoyed them!