I used a 13x9 inch pan for the cake and made the limbs and tail out of rice krispy treats. http://www.wubbzy.com/ has a printable template you could use of a Wubbzy with a curly tail. It is just cake but I thought it was too small and wasted too much cake so I drew my own templates.
To make the krispy parts I laid wax paper over the templates, and wearing gloves sprayed with cooking oil, I shaped the cereal. The limbs sat over night to be stiffer and I used wooden skewers broken into a couple inches (watch for splinters!) to attach them to the cake that was cut for the ears : )
The face I did freehand, and because I couldn't find black or even chocolate decorating icing I mixed blue, green, and red and used a butter knife : P
Katie, my daughter, is so sweet she even liked her cake : ) We had cake and then opened presents and after that she wanted to see "Wubbzy" again. It made this Momma's day : D
If you'd like to make this, here are the templates I used.