Are you allowed to play a 5 of a kind in Exploding Kittens to add an Exploding Kitten to your hand?
In the rules, 


  Five Different Cards
  
  If you play 5 different cards (any 5 cards with different titles), go
  through the Discard Pile to take any single card you’d like. (Grab the
  Pile quickly to choose your card so that you don’t get “Noped!”)


So you could probably grab an exploding kitten. But why should you:


  Exploding Kitten 4 Cards
  
  You must show this card immediately. Unless you have a Defuse Card,
  you’re dead. Discard all of your cards, including the Exploding
  Kitten.


So two things can happen: 


You have a defuse card. Use it and put the kitten back in the game.
You don't have a defuse card, you are out of the game.


The second option is a creative way to leave the game early. The first is possible a valid option if there is only one player left and you know for sure your defuse card was the last in the game and all attack and skip cards are gone. So by putting the kitten on top of the stack, you force him to draw and explode resulting in a win for you.