My daughter wanted a Siamese Cat Birthday Cake for her 6th birthday. I made three chocolate cakes (23cm round, 23cm square and a 12cm square) ahead of time and froze them. I used the round cake cut in half upright for the main body and carved the other pieces from the remaining two cakes, using the small one for the head. I stuck it all together with raspberry jam, and toothpicks for the ears, crumb coated it and froze it again.
I spread the whole cake with buttercream frosting first, then used a #233 grass tip for the fur (inspired by cat 45 on this site). I used various other tips to do the tail, paws and face details. The eyes are cut from blue gummy fish lollies with a bit of licorice on top. I found that the tiniest dab of white frosting on the licorice really brought the eyes to life.
I made whiskers from strands of toffee. I dug out a bit of cake from the sides of the face and filled with soft frosting so I could stick the whiskers in without them breaking. I made the mistake of freezing the cake again after this step and the condensation made some of the whiskers melt and drop off.