I've done a 3d Blues Clues cake many, many moons ago.
I used a wondermold for the butt, and 2 6" heart cakes turned upside down for the head. Carve the forehead from the front heart cake and round the tips to make the top of the head. I used a 6" round cut in half, place one cut side down on board to make the neck/body.
I covered mine in fondant, and made fondant paws and features. For the ears, I used pastillage but you can use styrofoam plates that are cut to shape and inserted into the side of the head.
For the spots I used cut out fondant shapes. The tail was made from a piece of gumpaste on a dowel rod.
Turn the heart upside down, with the double arches touching the board and the pointy end up. Carve the first heart with a forehead so basically taking off the top portion with the pointy end, leaving 2 rounded cheeks with the 2 arches.
I just PM'ed you a picture of the cake I did.
I made a 3d dog cake in my photos. I was a black Lab & im not sure if you're gonna be able to see all the details. Since it was all black its a bit difficult. But check out my dog and if you like it i can tell you how i made it and hopefully it'll help you. http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=666623
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