This one isn't a cupcake but it has some inside it!
I should have done this recipe on April 1rst! :)

This idea from the Wilton website. Instructions are there as well.
Although they do try to sell you their stuff on this site, there are some pretty cool ideas there too.

Candy melting wafers (also called candy melts) can be bought online (often as Wilton brand or Merckens) or in certain crafts stores in the USA and Canada. I don't know if/where they have them in other countries.