On the level Hot-Head Hop first kill th rat that you see, then go up to the guy in the barrel and get him to chase you to the place where you startred the level. There is a chest on top of the cave entrance; jump on him to get to it. It will have 2 lives in it; after you collect them, go jump into the lava to start again. It is slow but you can do this as much as you want.