Groucho Marx, the man who made a career of insulting people while making them laugh, was a unique comic.

The Groucho story, captured in a one-man show starring Gabe Kaplan, is mostly a string of one-line pearls. It was produced originally by Tomorrow Entertainment for HBO. Now J2 Communications has released this 90-minute special ($29.95) under the title "Gabe Kaplan As Groucho."

Kaplan, of "Welcome Back Kotter" renown, offers an astounding performance and likeness to Groucho's movements about the stage. Groucho's son Arthur Marx (who as a junior tennis player once beat Jack Kramer) co-authored the story.

Most of all, Kaplan makes you laugh, even while meandering through the no-so-funny and not-so-happy parts of Groucho's life. His timing is excellent. It's impeccable Groucho. And no matter how much you enjoyed Groucho's movies or his radio and television shows, there's a lot about the man that you'll likely find new.

His relationship with his four brothers, Chico, Harpo, Gummo and Zeppo, provides fertile material, and there are some classically crafted lines about his wives, friends and enemies.

The lacerating humor yields somewhat to Kaplan's strong finish when he delivers the lines of an 87-year-old debauchee. But the laughs don't stop. At times they pour forth faster than they did in the Marx Brothers' early stage shows, "I'll Say She Is," "Cocoanuts" and "Animal Crackers." Some lines are lifted from those shows and the movies that followed, such as "Monkey Business," "Horse Feathers," "Duck Soup," "A Night at the Opera," "A Day at the Races" and "A Night in Casablanca." Most of these were flops when released, but it gave Groucho great satisfaction to see them connect when re-released many years later to a new generation of fans.

Down and out at 57, Marx started a new career on television on a show he didn't feel had a chance. Putting his ad-lib abilities to superb use, he found that "You Bet Your Life" became a hit that lifted his career to new heights and lasted for 14 years. He was 82 when he did a special at Carnegie Hall.

A most touching scene is when Groucho talks about the passing of Harpo: "He was special, and I never got around to telling him how much I loved him."