He weighed 10 pounds at birth.
In the fourth grade, he was 5 feet 10 and 200 pounds.
He was banned from using the playground swings.
"I broke a swing when I was in elementary school," he said, sheepishly. "It's a tragedy."
As a student at Kaumualii Elementary on Kaua'i, he was assigned to a special section.
"Everybody had a little orange chair," Watson said. "I had a big brown teacher's chair at my desk. I guess there were perks. It was nice to have a big chair."
In the sixth grade, he was 6 feet.
As a freshman at Kaua'i High, he was 6-2 — and shaving regularly.
"I was a man-child," Watson said.
"When I was a freshman, everybody thought I was a senior," he said.
He transferred to Nanakuli High, where Leona — his classmate and future wife — also thought he was a senior. She realized he was younger when they were in the same world geography and Hawaiian classes the next year.
As a Nanakuli senior, he grew out his sideburns. Then he grew a goatee.
"I had more facial hair than my teachers," he said, smiling.
The perception did not change when he went to UH.
"My freshman year, on senior night, everybody's parents were giving me leis," Watson said. "They thought I was a senior. It's happened every year since I've been here. I always get a lei on senior night from random people."
Even teammates were fooled.
"The first time I saw him was my first day of training camp (last year)," defensive tackle Josh Leonard said. "I thought he was, like, 25. I didn't find out he wasn't a senior until our first game (of 2007)."