I used white candy melts or dipping and blue food colouring.
For the cake inside you can use any recipe you want!.
The trick(for me) is to make a syrup by combining powdered sugar and water and add this to the crumbled cake.
This will make sure that your cake pops wont fall apart.
After that you make any shape that you want by using the cake mixture as clay and adding a lollipop (cakepop) stick.
Prepare your candy melts by melting them(duh) and start dipping!
I find it helps a lot to have a piece of styrofoam nearby so you dont have to hold your pops till they dry.
I had to improvice and use that green thing, that is used to create centerpieces or whatever. (English is not my main language XD)
For the mouths you can use cacoabutter or a food pencil, but I improviced (again) by using food colouring and a toothpick.
There are lots of tutorials and ideas online, so browse a bit to find out wat works best for you.