For this Elmo Birthday Cake I used a Wilton Teddy Bear cake mold. I prepared it using the one box of pound cake and one box of pineapple cake mix. Follow the instructions provided on the box or on their website. I do not recommend placing the insert to make a hollow cake. It just makes the cake unstable.
The patch you see is from a hole in the cake when you use the insert if its not perfectly centered. Allow cake to cool in pan for 15-20 minutes before removing it from the cake pan. Also I kept the pan face up so the moisture could travel to the face so that just in case the cake stuck to the pan it was a part I was going to trim later.
After allowing cake to cool I kept it in the freezer for an hour so that it could harden. While in the freezer I prepared the Wilton recipe for the butter cream frosting and added red and orange food coloring. I set this in the fridge for later. After freezing I carved off the ears and the legs and used rice crispy treats to mold the arms and the legs. I left him like this for a few days.
The day before my son's birthday I went ahead and decorated with frosting, added coconut with green food coloring so it can look like Elmo was sitting on grass and moulded his eyes out of white fondant. I dyed a small amount of fondant black for the dark part of his eyes and a little orange for his nose. I think it came out better on my practice cake than on the real cake.
For the block I cut out some cake into a square and used tracing paper on fondant for the letter and the edges. It came out nice. Cookie cutters were also very useful.