Whenever you cast a green creature spell, you may search your library for a creature card, reveal it, then shuffle and put that card on top.
Whenever you cast a blue creature spell, reveal the top card of your library. If it’s a creature card, put that card into your hand.
If you cast a green and blue creature spell, both abilities will trigger. The abilities may be stacked so that when they resolve, you search your library for a creature card, put it on top of your library, and then put that card into your hand. The abilities may also be stacked in the other order, of course.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.