When Fists of Ironwood enters the battlefield, create two 1/1 green Saproling creature tokens.
Enchanted creature has trample.
3/14/2017 You create the Saproling tokens, even if Fists of Ironwood enters the battlefield attached to another player’s creature.
3/14/2017 The Saproling tokens aren’t created until after Fists of Ironwood is on the battlefield, so you can’t cast Fists of Ironwood on one of those tokens.
3/14/2017 If the target creature is an illegal target when Fists of Ironwood tries to resolve, Fists of Ironwood won’t resolve and won’t enter the battlefield. You won’t create Saproling tokens.