In February 1997, seven weeks after the crash that had put him in a Tallahassee hospital, Dan Cassill stirred in bed.

An episode of Seinfeld, the high school student's favorite show, had just aired on the television in his room.

His mother, Deby Cassill, had turned off the television and hugged him good night when Mr. Cassill whispered the three most important words of his young life: "Where am I?"

In the months to come, tabloids and national television shows such as Leeza and Maury Povich would interview Mr. Cassill and his mother, a University of South Florida St. Petersburg biologist, about that epiphany.

"Seinfeld wakes boy from coma," the Globe celebrity tabloid proclaimed.

It was true, yet it wasn't.

In the weeks since his sporty Mustang wrapped itself around a tree, Mr. Cassill had been able to answer simple questions from staffers by holding up one finger for yes or two for no. When asked to identify the ceiling, he pointed upward.

But he had not spoken or realized where he was.

Nonetheless, the Seinfeld experience was an important breakthrough moment. Mr. Cassill would cobble together a lengthy recovery punctuated with job losses, drug dependency, an arrest for fighting and fractured friendships.

He chronicled those struggles in his self-published book released in January, The Seinfeld Coma Kid's Afterlife. It is a straightforward account of mental challenges and personality changes brought on by his head injury from the crash, including a dependence on cigarettes that increased over time. Mr. Cassill died Feb. 22 in a Clearwater rehabilitation center of chronic obstructive pulmonary disease, or COPD. He was 34.

Before the crash, Mr. Cassill was a 17-year-old Panama City, Fla., native whose family had since moved to Tallahassee. His father, Paul Cassill, had taken his own life two years earlier.

On Dec. 12, 1996, Mr. Cassill was heading home after school in a drizzle when he passed a van in his souped-up Mustang. The car slid, then wrapped around an oak tree. The crash, Mr. Cassill wrote, "scrambled my brain like dropping a completed jigsaw puzzle."

"Some pieces break apart, some stick together, some are lost forever. It's dark in the place that they fall … "

An occasional smoker before the wreck, Mr. Cassill pestered the staff of Health South Rehabilitation Hospital for cigarettes as he recovered. In April 1997, he flew to California for the Leeza show, during which he asked host Leeza Gibbons to marry him.

They did Maury Povich's show in September, just as Mr. Cassill was also returning to Leon High to finish his junior year. But he was not the same student.

The new Mr. Cassill could not seem to control his behavior. He disrupted classes, swore at teachers and was expelled midway through the semester.

"I can confirm, from my own personal experience," he writes, "that this head injury had wiped out just about all the social skill I had gained by age 17. In essence, I was starting all over again from ground zero."

Later, he got kicked out of a community college in Arizona, where he had earned mostly A's. A litany of troubles followed. Mr. Cassill tried too hard to make friends with women and ended up putting them off. His persistence in applying for jobs sometimes got him hired, but he had trouble. He fell prey to bullies — or, in one case, a man who introduced him to crack cocaine but wanted sex in return.

In 2003, he told his mother about the crack. She brought him back to St. Petersburg, he joined AA and began a more peaceful period.

"On his good days he was funny as hell," said Mike Heath, 44, a friend he met in recovery circles. "He'd make you laugh. That's why I enjoyed hanging around with him."

At other times Mr. Cassill seemed "out there" and delusional, Heath said.

His mental setbacks did not extend to remembering names. The book is littered with them. Every teacher or administrator, health worker, co-worker, roommate or friend who shows up in Mr. Cassill's book is named. Deby Cassill, an expert on the behavior of fire ants, said her son's memory was better than hers.

The missing piece, she said, was something more personal.

"He had forgotten how to make friends," his mother said. "You smile. You make eye contact with people. You shake hands."

Some people with serious head injuries "have to relearn that," she said.

In 2008, a motorist collided with Mr. Cassill's bicycle, then ran over his foot. Mr. Cassill was hospitalized, then in a wheelchair for two months, during which time his cigarette smoking increased.

He developed COPD and suffered collapsed lungs several times. Mr. Cassill eventually moved to Advanced Health and Rehabilitation Center in Clearwater.

"I am free to smoke and drink coffee as much as I want," he wrote. "Pizza and sodas are delivered to my door with a phone call."

Mr. Cassill enjoyed the routine so much, he declined his mother's offer of moving him closer to St. Petersburg. He went through a case of 2-liter Mountain Dew bottles every few days, and introduced himself to new patients.

In January, a month before his death, Mr. Cassill added a brief epilogue to his book.

"They say that coming out of a coma is like being born a second time," he wrote. "My second life has been one crazy ride and it isn't over yet."

At long last, that long and bumpy ride appeared to be smoothing itself out.

Andrew Meacham can be reached at ameacham@tampabay.com or (727) 892-2248.