Preheat the oven to 180 degrees C. Line a muffin tin with patty cups.
In a large bowl, cream butter and sugar. Beat in eggs, one at a time. Add lemon rind and vanilla; mix well.
In a separate bowl, combine flour, bicarb, baking powder and salt. Add to creamed mixture alternately with sour cream (cake mixture will be thick). Fill the patty cups 3/4 full. Bake the cakes in the preheated oven for 25-30 minutes or until a skewer inserted near the centre comes out clean. Cool for 10 minutes; remove to wire racks to cool completely.
Meanwhile make the icing: In a large bowl, cream together the butter and vanilla. Blend in the sugar, a quarter at a time, beating well after each addition. Beat in the milk, and continue mixing until light and fluffy.
To make the ears; take the marshmallow halves and place them on a clean surface, cut side down. Spread a little bit of icing over the top of each. Then sprinkle with the pink decorating sugar.
When the cakes are cool, spread an even layer of icing over each. Then take the prepared marshmallow halves and carefully place two on each cake to make the ears. Finally, make the face by putting a smartie in the middle for a nose, and then drawing eyes and whiskers with the black writing icing.