When you start the game, on the screen where it tells you about the iPhone app, if you look to the left, theres a demon putting a mushroom into a bomb.
When you scroll over the bubbles on the bottom of the screen, you should be able to see a little thumbnail of the unit, the attack, life, etc. +1 if you agree.
Suggestion: Hero skills, I.E. for popo, +5 attack for dwarf engineers. i just started playing so i only have him and the other starter one. but i think all(or most) should have some 'skill' or 'attribute'. now i could be wrong, some might. like i said, i just started the game.