Prepare cake mix adding eggs and oil exactly as box directs. Substitute root beer for water called for. Add root beer extract if using. Pour batter into a greased 9 by 13 pan and bake as directed on box. Cool.
For root beer float topping: Prepare Dream Whip with root beer substituted for the milk. Use both envelopes of Dream Whip to make a good amount of topping. Chill well.
To serve: Cut cake into squares and place a large amount of topping on cake.
NOTE: Let root beer sit a few minutes before measuring to assure accuracy. It bubbles so much you can end up with a dry cake if you don't give it a chance to release the bubbles. The flavor of this cake is light and most people like it but I actually like a stronger flavor and added the extract to the cake mix because of that.