If you have a large area of dirt in your yard that just doesn't like to grow grass, I say take advantage of it.
Some dinosaurs came out to fight the army men that were defending the castle.
Note to anyone who may try this sort of thing: Only let your kids use toys that you don't mind never seeing again since they may very well sink into the mud. I thought I had warned my kids about this, but there is a missing Power Ranger who may have had some tears cried over his loss.
Sometimes you just need to get muddy.