Cecil Williams II carries two personalities rolled into one 6-foot-4, 210-pound package.
By day, he is a bookworm preparing to enter his senior year at Laguna Creek High School.
He has a 4.3 grade-point average in the school's International Baccalaureate program, which he describes as "academics on steroids."
Williams committed to Harvard this week to study neuroscience and play quarterback.
Come Friday nights this fall, Williams will transform, full moon or otherwise. The charm will turn to ferocity.
"His favorite thing in football is to bust up the wedge on special teams," Laguna Creek coach Dave Morton said. "We think, 'Holy cow. Where's the thinker, the cognitive kid?' because there he is blowing kids up in pads."
Morton, who has coached football locally for more than 30 years, said a scholar and talent like Williams comes around once a career.
"I was telling the Harvard coach, 'Wait until you really get to know Cecil because you'll love him,' " Morton said. "I was in tears because I was so elated for him about Harvard. He's everything you'd ever want in a student-athlete."
Williams said of his dual personality: "I'm only wild in football. There's a time and place to act that way, and football is a great outlet."
So what does one do, exactly, with a neuroscience degree?
And what is it, again?
"It's a study of the brain," said Williams. "I want to be a surgeon and help find a cure for Alzheimer's and other mental diseases. I've always been fascinated by science."
Williams originally was interested in law but decided he didn't want to argue for a living. He wants to save lives.
"I want to make an impact," he said. "I think I can do that."
First, he pledges to give Laguna Creek's offense a much-needed boost.
The Cardinals scored eight or fewer points eight times during a 2-8 season last year, with Williams accounting for 11 touchdowns.
Williams and Morton vow to make this season one to cherish.
"We'll be a lot better," the quarterback said.
While he also plays basketball and baseball, Williams comes from a football family.
His father played wide receiver at Sacramento High in the late 1970s, and tight end and wide receiver at Sacramento State.
Cecil Williams had a taste of the NFL with the 49ers (training camp), Chiefs and Chargers (practice squad and strike-shortened season in 1987).
Williams regards his son as a trendsetter for his siblings.
"The template has been made," Williams said with a hearty laugh. "As parents, we're beaming and extremely proud of Cecil for the Harvard commitment. I'm his toughest critic and greatest supporter. What he hasn't done is have a breakout year, and the timing is right now.
"There's no worry or concern now about college. He knows where he's going. Now, just go out, stay healthy, compete hard and have some fun."
And wedge-busting is always a fun way to kick off a game and season.