Easy "Superbounce" achievement
Play Toyland Act two. Just after the first jack-in-the-box is a straight area where two toy soldiers spawn, followed by a toy airplane, a juggler, two more toy soldiers, and finally a mid-air Jack-in-the-box. Bounce on all seven of them (avoid the unicycle that appears when the juggler is hit). Because the timing is difficult, a few attempts may be required.
Easy lives
Go up the stairs to the second floor. Progress until reaching the back wall. Floating above the bench is an extra life. Enter any level, and after it loads pause game play, then choose to return to the castle. You will now have one more life. Repeat the process as many times as desired. Note: Stars will not carry over.