My girlfriend wants me to make a cake like this for her daughters birthday next month. She REALLY wants the cat on top, so how do i do it? Carve it out of cake, or RKT?

I would do RTK, especially if you ant the tail to stand up like that. Also, if you do RTK you can make it ahead of time. Good luck.

RTK is good idea for this. with RTK it can be done easily.

I agree with using RKT. That way you can do it ahead and have plenty of time to get it right and not feel pressured.