I made this topper just for a tutorial purpose... If I were to do it for a cake I would make the whole figure on a cake dummy/piece of styrofoam and I would insert a barbecue skewer all the way down to the bottom of the styrofoam (lenght of skewer in the styrofoam = height of cake). As it goes for the element shown on the photo, I would place it on a cake just before putting the figure on the cake :)
Roll a sausage and flatten the ends. Use a ball tool to hollow out the ends as shown on the photo.
Pinch the edges to make them thinner.
If the tail is too heavy you can insert a wire inside to support it.
Add a few details...
... DONE! :)
Topper inspired by Adam Record's illustration - https://pl.pinterest.com/pin/120189883781446120/