I created a Skylanders-themed birthday cake for my son's 8th birthday party. I referenced a lot of pins on Pinterest and designed my own take on it. Bottom two photos are in progress, top two photos are finished product.

Time required:
I spent a total of approximately 3 hours baking cakes, and 4 hours assembling and frosting the cake.

Materials:
Cake mix, and associated ingredients including substitutions mentioned above
Cake frosting (I used 5 canisters for this cake.)
Candies to decorate (be creative!)
Large marshmallows
Candy eyes (from Wilton, available where they sell cake decorating supplies)
Frosting bags/tips (I have a little plastic plunger style frosting kit that I've used for years)
Jellybeans
Any decorative icing (the writing is a sparkle blue icing)
Vanilla wafers for "sand"
Mini-marshmallows for sheep
Cupcake liners for sheep

On frosting: buy more cans than you think you'll need, so you don't run out at 11:30pm and have to run to a 24 hour grocery store to get more. Ask me how I know :\

Step 1: How I Made It

I used standard cake mixes (4 total), altering the ingredients as follows:
Oil - replace with melted and cooled butter
Eggs - add 1 egg to recommended number
Water - replace with buttermilk, milk or whey. I used buttermilk in the chocolate cake, and a combination of buttermilk, whey and milk in the vanilla and red velvet cake mixes.

I used 2 chocolate cake mixes, 1 vanilla, and 1 red velvet. The outlying islands are red velvet and vanilla swirled together, and the sheep cupcakes are the same. The main body of the cake is chocolate, with the topmost layer made of red velvet/vanilla.

I baked 1 rectangular (9"x13") layer (choc), 3 round (9") layers (2 choc, 1 red velvet/vanilla), and 1 round (6"x4" high) layer (red velvet/vanilla).

I placed the rectangular layer on my cake board (recycled cardboard box, strengthened and covered with aluminum foil) towards the upper left corner. I placed a chocolate round on top of the upper right corner of the rectangle, so that part of the round was off the rectangle. I then used a table knife to cut the rectangular cake to match the round. I removed the upper corner of the rectangular cake and then put the round in its place. This left me with a rectangular cake that had a round bubble at the same level on its upper right corner.

I placed a second chocolate round on top of the first one, giving me 2 layers high. I then placed the smaller round (6") of red velvet/vanilla on the top of the second round, giving me three layers. I cut squares from the 9" red velvet round to make the outlying islands.

I did a milk chocolate crumb coat on all the layers and reassembled the cake. Grass and water is tinted vanilla frosting, piped through a decorating tool with a large star-shaped tip. I used a variety of candies from Aldi: small square chocolates for the fountain walls, Jive (similar to Twix) candies for the short walls, Pirouline-style wafers for the striped walls, and milk chocolate bars for the bridges. I used large roasting marshmallows for the white walls. The sand is crushed vanilla wafers, applied onto a layer of chocolate frosting to help it stay in place. I used jellybeans for rocks, and placed circles of wax paper in four different spots so I could place Skylander figures for the party. The sheep on the cake is a leftover half of a marshmallow that I piped some chocolate frosting on and put candy eyes in.

The cupcakes are red velvet/vanilla, with white vanilla frosting. I stuck mini marshmallows onto it, and a small triangle of leftover chocolate cake. I piped some chocolate frosting on the cake and then stuck candy eyes onto the frosting.

This was a lot of fun to make and almost felt like cheating when you pipe some frosting on the sides to "glue" the candies into place. So much less work!