Simple, yes. Quick? No. I don't make cakes as often as I used to and I'm out of practice...but I needed a few different colors of frosting and made the ears from chocolate so those elements took some time.
I used three layers of six inch cake to make a tallish stack.
I've seen some unicorn cakes with a horn made of fondant or chocolate, but I found this swirled lollipop for $1 at Walmart and never looked back.
I used the Wilton ColorSwirl 3 Color Coupler to add the mane (I only used two colors). It works great once it's all set up and ready to pipe, but getting the bags of frosting situated took some patience. Next time I will load less frosting into each bag and refill if needed - I think that would make the pieces easier to fit together and less likely to come apart.
Once it was all assembled, I dusted the cake liberally with disco dust for some added flair. I love that stuff - it really makes a difference, especially on a cake decorated like a magical creature.
I'll do this one again at some point - it was perfect for a smaller dessert and was pretty cute if I do say so myself.