Credit: Peter Andrew Bosch, The Miami Herald/AP Photo

ABC News' Yunji De Nies and Olivia Katrandjian report:

The four-time NBA champion Shaquille O'Neal donned a cap and bright red XXXL-sized gown to receive his doctorate degree from Barry University Saturday in Miami, Florida.

On stage, he showed his enthusiasm in a way only someone over seven feet tall can do, by lifting his professor into the air.

After leaving Louisiana State University early for the NBA, Shaq went back to school and earned his bachelor's degree and then a master's degree and now, a doctorate in education.

O'Neal told ABC News there are three reasons he hasn't just kicked his feet up and lounged on an island since his retirement.

"One, I promised my parents I would[follow my passion for education]. Two, I wanted to continue my education and three, I wanted to challenge myself," he said.

"The hardest part was getting back into high school mode. You ever have that high school teacher that says, you've got to read six chapters over the weekend?" he said.

He wrote his thesis on the value of humor in leadership, because he says he's a natural leader who loves to laugh.

The graduate wants to become a motivational speaker and plans to go to law school.

O'Neal told ABC News there's "no way" anyone is allowed to call him Shaq anymore.

"Only the children can call me Shaq, the adults have to address me as Dr. O'Neal," he said.

"I'm proud to call you Dr. O'Neal!" said his mother.

A year into retirement, after 19 seasons on the court, Dr. O'Neal is not looking back. He says he doesn't miss the game "Because I got a new walk, a doctor's walk."