My son and second born turns 4 today. We found with our first child that 4 was a delightful age and I've been looking forward to it with the boy.
This year, and for the previous two birthdays, my wife made custom super hero shirts for the boy to wear. When he turned 2, we came up with "Two-perman."
Last year, she made him a "RO3IN" shirt.
This year, for his fourth birthday, he became "The 4lash."
There are already ideas percolating for what his 5th birthday could be. We'll see how long the tradition keeps up. My wife could be still making these when he's 18 or this could wrap up in the next couple years.
Either way, happy birthday to my little super hero!