Sickle, The Doofosaurus-Rex

When Sickle, The Doofosaurus-Rex enters the battlefield, choose dirps or cats
If you chose dirps, each creature you control has {t}look at the top card of your library, you may play
it for half of it's mana cost rounded up, otherwise it
goes in the graveyard
If you chose cats, each creature you control has{t}create X 1/1 white cat creature tokens, where X is
it's converted mana cost.