|The problem area|
You can usually fix little problems like this. Keep in mind, though, that fixing fondant will never look as good as a full, unblemished sheet, and sometimes you just need to start over.
I had a little issue with the hippo cake that I did a couple of weeks ago. I had put the fondant on it, and because the cakes were strange shapes, I needed to really work it to get the hippos covered completely.
|Adding the spackle|
This method worked fine in this case, but it was a hippo anyway, and it didn't need to be perfectly smooth. Sometimes it's better to start over, but it's important to know what your fixing-it options are!