Only a few entertainers have careers that span decades and display multiple skills as performers, writers, directors and producers. An even smaller number become synonymous with a charitable cause. Only one has raised billions of dollars for such a cause.

That entertainer is Jerry Lewis.

Touted for his mastery of slapstick and clownish pratfalls, Lewis was born Joseph Levitch in Newark, N.J., and achieved early fame as half of the Martin and Lewis comedy team, where Lewis played the zany one to crooner Dean Martin’s straight man. Their Copacabana nightclub act and a 1948 appearance on “The Ed Sullivan Show” landed the duo a string of successful Hal Wallis laffers for Paramount, including “My Friend Irma Goes West,” “At War With the Army” and “Sailor Beware.”

Lewis later embarked on a solo career as an actor-writer-director-producer that has stretched across some 65 years and spawned such classic screwball comedies as “The Nutty Professor,” “The Family Jewels” and “The Bellboy.”

“He’s as iconic as Bugs Bunny,” says Daniel Noah, who directed Lewis in the 2013 drama “Max Rose.” “When he agreed to be in the film I was very nervous because not only is Jerry one of the greatest movie stars to have ever appeared onscreen, but he is an extremely accomplished director and producer and writer. When I met him he instantly took on the role of a friend and mentor.”

For Michael Klastorin, who served as the publicist on “Max,” working with Lewis, whom he considers one of his “childhood heroes,” was “everything (he) hoped it would be.”

“The first day of production we gathered the entire cast and crew and he welcomed everybody personally,” he remembers. “Within three days he knew the names of everybody on the set. His work ethic was spectacular. I can’t remember somebody being so involved in a project as Jerry. He invests all of his energy and talent and his love in every project that he undertakes.”

This dedication is especially evident in “The King of Comedy,” Martin Scorsese’s searing black comedy about an obsessed fan (Robert De Niro) who kidnaps a popular latenight talkshow host, a role that required Lewis to mine his satirical side.

“Jerry has an incredible sense of timing,” marvels editor Thelma Schoonmaker, who worked with him on the 1982 film. “He would say to the actors, ‘Wait, count to three before you answer me.’ Or ‘Say half the sentence and then count to three and then answer me.’ It was fascinating for me to watch (how) he was training people to do classic comic timing.”

Per Leonard Morpurgo, former head of European publicity at Columbia, Lewis’ generosity extends off-set as well.

“It was 1965 and I was having dinner with George Segal at the Lido in Paris when a waiter brought us a bottle of champagne offered by ‘that gentleman,’ ” he recalls. “He pointed to Jerry Lewis. I went over to Jerry, told him who I was and thanked him. A few weeks later Jerry ended his multiyear contract with Paramount and moved to Columbia. I joked to anyone who’d listen that I was responsible, of course.”

But Lewis’ crowning achievement is undoubtedly his 44-year-long run as founder and host of the Muscular Dystrophy Assn. telethon, which has raised billions of dollars for medical research of the disease.

“He is a very caring person,” Klastorin says. “He has very heartfelt beliefs and causes, and he gives of himself 100% to those causes. I don’t believe Jerry Lewis to be capable of doing anything on a casual basis — either as an entertainer, a filmmaker or a humanitarian.”