A CHARACTER YOU WILL NEVER FORGET - "60 MINUTES" SUNDAY ON CBS

The Holland College Golden Knights men's basketball team is a powerhouse of collegiate sports. It's played in 10 NCAA championships, winning five. It boasts a list of memorable players like 350-pound center Isaac Mosely, forwards Otis Pookie and Brad Jasmin and a guy nicknamed "Slappy," whose real name is Sean. But the Golden Knights have never played a real game on a real court. They play all their games inside the brain of a man capable of remembering virtually every day of his life and every one of more than 50 seasons of imaginary Golden Knight basketball. Meet Bob Petrella, the Golden Knights' biggest and only fan, and one of only 56 persons known to have a mysterious condition called highly superior autobiographical memory. He is a character you will never forget. Petrella tells his story to Lesley Stahl on the next edition of 60 MINUTES, Sunday April 19 (7:00-8:00 PM, ET/PT) on the CBS Television Network.

Petrella remembers the day he conjured his college basketball team. "I was 13, January 3, 1964. It was a Friday," he says. Each year ever since, it changes, just like real life. "When they're seniors, they graduate so we bring in new classes," he says, "Which is always kind of fun for me, because it's kind of like having a new kid or something," laughs Petrella. Watch an excerpt.

Just a handful of close friends know about Petrella's imaginary team. Bobby Simmons tells Stahl he will hear of news of the Golden Knights from his friend. "[Petrella] will send me an email and say 'Travis Shakespeare died in a one-car accident on an icy road outside Philadelphia' and it's heartbreaking," says Simmons with a smile. Then he laughs, "It's like, oh no, I loved this guy and he's gone!"

Like others with HSAM, Petrella has obsessions, including the urge to wash his keys if he drops them. But these individuals are not autistic; they live ordinary lives. Dr. James McGaugh, a leading authority in memory and cognition at the University of California Irvine, has studied the 56 people identified with HSAM and says none to his knowledge has created such a fantasy world.

Is the Holland College team an obsession? "I guess you could say the fantasy team is another form of obsession," he tells Stahl, but a harmless one. "In some sense, it's a good idea to have an imaginary basketball team because it doesn't cost anything and it's a lot of fun."