O'Mahoney
If you have the last name O'Mahoney, you're the smartest and most awesome person in the room. If you don't put the apostrophe, you're a complete idiot.
O'Mahoney? No apostrophe? I'm gonna cry.
You're not O'Mahoney. You're just a dummy.
No apostrophe? That's not O'Mahoney. That's just trash.