Go to any place with a boulder that Chunky can pick up, either as his normal self or when he's large. Hold down the B button to charge up your attack and then run into the boulder. Immediately after you pick it up, release the B button. You'll throw the boulder and afterwards you will be holding your arms out holding nothing. In some cases, you'll be able to walk around like this. In others, the boulder will appear in your arms. And in others (such as the large boulder in Crystal Caves that requires large Chunky), you'll be stuck in one place until you throw the boulder - and then it'll be floating. You can jump into it after that. And if you grab a floating one and throw it, it will reappear, still floating. And, if you walk out of an area with your arms out without a rock, the game will freeze. Tons of fun.