%People let me tell you 'bout my best friend He's a one-boy cuddly toy My up my down, my pride and joy People let me tell you about him, he's so much fun Whether we're talking man to man or whether we're talking son to son 'Cause he's my best friend . . . --From "Best Friend," the theme from "The Courtship of Eddie's Father," by Harry Nilsson

BRANDON CRUZ spent most of his wonder years, ages 6 through 10, on a television sound stage. On the hit ABC series "The Courtship of Eddie's Father," Cruz played the freckle-faced, matchmaking, remarkably reflective Eddie Corbett, only son, caretaker and best friend of widowed, worried magazine publisher Tom Corbett, played by Bill Bixby.

"A lot of people still remember me that way, as that little kid," says Cruz, now 20. "So people that are punk-rockers, like, trip out when they meet me. And people who recognize me from TV go crazy when they find out I'm into punk."

"Mr. Eddie's Father" and housekeeper Mrs. Livingston might be wondering what happened to their little Eddie; their level-headed charge has grown up to be the lead singer in a punk-rock band called "Doctor Know."

"I guess you could call us punk to the extreme," Cruz says, describing his music as "really fast statements of social realities." Cruz, who writes most of the songs with his guitarist and bass player, laments the limitations of the punk genre for the budding songwriter. "You can't really understand the lyrics because it's such a frantic pace, but they have a lot of meaning to me."

Cruz got his start on the small screen at age 6, when his mom spotted an ad and trundled him off to a tryout for television commercials. His taped audition was noticed by a casting agent and he grew up as Eddie Corbett.

The gentle comedy series ran four seasons and provided Cruz with a dual education. "I had never been trained as an actor," he says. "Well, I was in a play -- I was Toto in 'The Wizard of Oz' when I was 4. But all I had to do was crawl around and bark.

"I didn't even know how to read when the show started. Bill Bixby pretty much taught me how to read on the set. I owe a lot to him. I just memorized the scripts a little at a time. I couldn't even use cue cards, because I couldn't read those, either."

Cruz says he also enjoyed working with fledgling actress Jodie Foster, another "Eddie" alumnus. "She played my best friend, Joey Kelly -- she was the tomboy who punched me out all the time."

After "Eddie's Father," Cruz kept busy with parts in "The Bad News Bears" and Henry Winkler's movie "The One and Only." Cruz says his career high point was working with Claire Bloom in "The Going Up of David Lev," a television movie for Israel's 25th anniversary.

"And I did an 'Incredible Hulk' with Bill. It was really fun because we hadn't worked together for seven years. I'd love to revive 'Eddie's Father,' " Cruz says, "you know, instead of the kid worrying about his father and getting him dates and everything, the father would be trying to keep me away from punk-rockers and things like that. I could still play a lot younger than 20--16 or 17 . . . "

Doctor Know (his second band; the first was called "The Eddys") takes up most of his time, when he's not "hanging out at the beach."

"We usually practice in my mom's living room," Cruz says, adding that she is pretty good-natured about it, being an artist herself. "I guess she figures it's good as long as we're not sitting around stagnating, playing Pac-Man . . . " Cruz laughs.

"I guess I'm not too sure about the future yet," Cruz says. "I'd like to get behind the scenes with TV and movies, produce, direct. I'd like that feeling of driving up to the gates of a big studio. I'm up for the lead in a major feature film, but that's still up in the air. And I'd like my band to really take off, but I don't think punk will last forever. But I grew up in the entertainment business, and I think I'll be in it for all my life."