Malcolm-Jamal Warner, an actor and artist who rose to fame as a child as Theodore Huxtable on “ The Cosby Show,” has died, according to a source close to the actor. He was 54.

Malcolm-Jamal Warner, an actor and artist who rose to fame as a child as Theodore Huxtable on “The Cosby Show,” died Sunday in a drowning accident in Costa Rica, according to local police.

Some of the greatest lessons about growing up and what it means to be an adult I learned from—or, rather, through—Theo Huxtable. The middle-child sibling on The Cosby Show, Theo was a conduit ...