There is no age limit on being silly and having a good time. Even at 100, you can laugh, joke around, and leave the grown-up behavior for another day.
It works well for a grandparent, relative, or friend celebrating a full century. Anyone who believes age should not change their personality can enjoy this simple reminder.
There is plenty to celebrate after 100 years, including the chance to keep being yourself. The best birthday plan may be to forget the rules and simply enjoy the day.