One day your walkingdown the street and you drop dead of a heart attack. When you get to heaven, God apologizes and says you were taken before your time. And to show he is sorry, he is going to allow you to return to earth under 2 different circumstances.
1) You will come back at the age of 21. Your body will never grow old and you will look like you are 21 until you die. The outside of your body will not age, but the inside will. All the plumbing will work too just like it did when you were 21. However you will be dirt poor for the rest of your life.
2) You will come back at the age of 21, but age at an excellerated rate. By the time your 30 you will look 50, and by the time your 50 you will look 80. However you will come back with a very large sum of money in your bank account.
3) He sends you to hell where Satan shoves pineapples up your ass.