Bobby Darin, pictured as himself and in Groucho Marx disguise on the TV Showtime cover, has found success in various theatrical endeavors during his career. By the age of 22 he had his first Gold Record and a year later was a Grammy Award winner voted Best New Artist. His recording of "Mack the Knife, released that year, was named Best Song.

Darin, who was born Walden Robert Cassotto, later achieved fame as a composer (Splish Splash), night club performer and actor. His current showcase is that of TV varienty show host, subbing as summer replacement for Dean Martin. The program, which was created by Martin's own Claude Productions, started August 27 for a five-week run. On it he not only sings but does comedy routines. Like most summer programs, it is being considered as a possible mid-season replacement.

During the years 1960 to 1964, Darin made seven films, the best known of which was Captain Newman, M.D., for which he won a Best Supporting Actor Oscar nomination and a French Film Critics award as Best Foreigh Actor.

He also starred as a Nazi mental patient in Pressure Point, a gun shy sheriff in Gunfight in Abilene and appeared wtih ex-wife Sandra Dee in the movie comedies, Come September, If a Man Answers and That Funny Feeling. He and the actress, the parents of a son, Dodd Mitchell, age 10, are now divorced.

A few years ago the singer attempted to alter his previous style by switching to blues and hard rock, but the move was only temporary. He even changed his name from "Bobby" to "Bob" for the occasion. The latter was his billing in his late film, The Happy Ending, which starred Jean Simmons.

Darin's career was curtailed considerably last year when he underwent open heart surgery. Now fully recovered, he is back in harness, engaged in a variety of new pursuits. Besides his summer series, he also was guest host for Johnny Carson recently. He also wrote, produced, scored and directed the upcoming move, The Vendors, scheduled for release this year.

Bobby Darin, a musical rage of the 1960's, isn't likely to go through the 1970's unnoticed.