Yellow Wollywog

Trample
When Yellow Wollywog enters the battlefield, you may draw a card. If you do, discard a card.
Metamorph {2}{u} ({2}{u}, Exile a creature you control that shared a creature type with Yellow Wollywog: You may cast Yellow Wollywog without paying its mana cost. Activate this ability only any time you could cast a sorcery.)