Greg

Greg Brown is a classmate of Fat Albert and the gang, who turns out to be a computer hacker. Hacking into other computer systems illegally. By the end, he learns his lesson and promises to never hack into other computers again. 

Computer Caper

Russell is on his way to the library to do research for his History report. There he encounters his classmate Greg Bowen who helps by taking him home to do the research on his computer. Russell becomes impressed with Greg's hardware and does so well on his report, but later learns he's a hacker who illegally gains access to other computers to steal data that's not rightfully his. Some time later, authorities from the police computer crime task force arrive at Greg's home as they've tracked his illegally accusing a hospital computer, significantly messing up their records. Greg runs off and the gang spots him at a train bridge. He falls off when a train passes by, landing on a beam, and is in danger of plummeting into certain doom should another train pass. He's rescued in time and while recovering at the hospital, he promises his mother and his friends that he'll never hack into other computers again. 

Cosby's Lesson on Computer Hackers

"Greg might not have time to explain, or maybe he didn't want to. A hacker is some what a thief. Hackers don't go around and breaking into people's houses, but what they do is just as wrong. Hackers use their computers and usually a phone line to connect into another person's computer system. And then they mess up all the information that's in the other computer. Hackers cause nothing but trouble, and it's a crime. And I hope Russell finds out about the serious problems hackers created before he gets into trouble."

trivia 
he is voiced by lane Scheimer the son of Lou Scheimer who voices Dumb Donald