To earn as many lives as you'd like, beat the Translyvania level. After placing the flag, summon the airplane and select Transylvania again. Find the extra life hidden under the first stack of barrels. To find the other life, jump into the water then go all the way to the end. When you've found both of them, return to the entrance and leave the castle. You many now re-enter the castle and collect another extra life. Repeat as needed.