Williams got his big break in 1978 when he auditioned to play alien Mork from the planet Ork on Happy Days, making a lasting first impression on producer Garry Marshall by sitting on his head when he was asked to take a seat. Mork proved to be so popular that it led to a spin-off, Mork & Mindy. Williams returned for a guest appearance in Season 6.

Nanu-nanu. Williams played Mork opposite Pam Dawber as human love interest and future wife Mindy for four seasons. Mork, and the show itself, was tailored to Williams' improvisation strengths and comedic abilities as an impressionist. Williams earned one Emmy nomination for Lead Actor in a Comedy Series, but lost to All in the Family's Carroll O'Connor.

Williams made his film debut in Robert Altman's live-action adaption of the spinach-eating sailor man comic strip. Expectations were high for the film with Williams' popularity peaking, but the film flopped at the box office.

Based on John Irving's novel of the same name, the film marked Williams' first foray into drama. He starred as the titular character, the illegitimate son of a feminist single mother, Jenny (Glenn Close, in her film debut), who tries to broaden Garp's outlook on life — going as far as to hire a hooker for him.

With that infectious, boisterous greeting, Williams, as Armed Forces radio DJ Adrian Cronauer, scored a hit with the Vietnam War comedy — along with a Golden Globe for Comedy/Musical Actor and his first of four Academy Award nominations. He lost the Best Actor Oscar to Michael Douglas in Wall Street.

"O captain! My captain!" Williams delivered one his most inspiring performances when he played prep school English teacher John Keating in this critically acclaimed and wildly successful drama. Through his performance, Williams taught his doe-eyed male students 7mdash; including Ethan Hawke and Josh Charles — and audiences around the world, to "carpe diem," aka seize the day. Williams was rewarded with his second Oscar nomination for Best Actor.

Williams continued to show his range in Penny Marshall's adaptation of neurologist Oliver Sacks' memoir. Playing the fictional Dr. Malcolm Sayer, who's pioneering a new drug for catatonic victims of encephalitis, Williams won the National Board of Review Award for Best Actor (tying with co-star Robert De Niro) and was nominated for a Golden Globe.

Williams earned his third Oscar nomination as Parry, a deranged homeless man who's determined to find the Holy Grail with the help of former shock jock Jack (Jeff Bridges), who's seeking redemption after unknowingly causing Parry's homelessness. Williams won his second Comedy/Musical Golden Globe, but lost the Oscar to Anthony Hopkins in The Silence of the Lambs.

Thanks to his limitless energy and whip-fast humor, it's hard to imagine Williams ever playing the responsible grown-up. But he did just that in this reimagining of Peter Pan, in which he portrayed an adult Peter. Now a family man and a workaholic, Peter must remember his magical childhood when he is forced to go back to Neverland to get back his children from the clutches of the evil Captain Hook.

The Disney hit remains one of Williams' most beloved movies because of his energetic and, pun fully intended, animated vocal portrayal of the titular character's BFF, the Genie. The actor even got to show off his musical talents on songs like "Prince Ali" and "Friend Like Me." The Hollywood Foreign Press Association gave Williams a special Golden Globe for his work.

Williams got deep into character — face mask, wig, fake boobs and all — for his role in the heartwarming family comedy. The actor won a Golden Globe award for his performance as Daniel, a newly divorced father of three who goes undercover as elderly housekeeper Euphegenia Doubtfire in order to stay close to his kids. The film was the second-most successful film of 1993, behind Jurassic Park, and reports about a sequel involving Williams resurfaced in April 2014.

Williams followed Mrs. Doubtfire with a drastically different film. The cerebral picture starred the actor as Hector, a man searching for his place in the world, and follows him through five incarnations centuries apart.

Williams again experimented with his look for the fantasy-adventure film, in which he starred as a young boy who has spent 26 years stuck in a jungle-themed board game. After two children unknowingly set him free, they band together to finish the game and undo all the damage the game has wrought.

Williams vamped it up in the underrated Mike Nichols romp as Armand Goldman, the owner of South Beach drag club The Birdcage who, along with his fabulously flamboyant partner Albert (Nathan Lane), agree to play straight to meet the conservative parents (Gene Hackman and Dianne Wiest) of their son's fiancé. The cast won the second-ever Screen Actors Guild Award for film ensemble.

A remake of The Absent-Minded Professor, the comedy starred Williams as Professor Philip Brainard, who discovers "flubber," a green, bouncy goo that has a mind of its own. Despite poor reviews, Flubber was a huge hit at the box office.

The Gus Van Sant film launched screenwriters and future movie stars Matt Damon and Ben Affleck onto the A list, but it also finally won an Oscar for Williams. After three nominations, Williams earned the Best Supporting Actor statuette for his performance as Sean, a brash behavioral therapist who encourages janitor-turned-MIT student Will Hunting (Damon) to open himself up to others, as Will helped Sean do the same after his wife's death.

Based on Richard Matheson's 1978 novel of the same name, the fantasy drama starred Williams as Chris, a man who dies in a car crash and searches for his dead wife in the afterlife with his friend Albert (Cuba Gooding Jr.).

Proving laughter is the best medicine, Williams charmed audiences as the real-life Dr. Hunter "Patch" Adams, who dresses up as clowns to cheer up his patients. Williams earned a Golden Globe nomination for his performance.

A remake of the 1975 German film Jakob der Lugner, the World War II drama starred Williams as the titular Polish-Jewish shopkeeper who, after overhearing a radio broadcast with good news, decides to spread fictional, optimistic stories to keep hope alive in the Polish ghetto. The film bombed at the box office and Williams was nominated for a Razzie.

Williams earned another Razzie nomination the same year for playing Andrew, an android who tries to acclimate to human life and emotions when he joins the Martin family in April 2005. The film based on Isaac Asimov's novella The Bicentennial Man.

Williams starred as disgraced kiddie TV host Rainbow Randolph, who gets fired and replaced with fast-rising star Sheldon "Smoochy the Rhino" Mopes (Edward Norton), and soon plots to bring down his younger rival. Williams received a Razzie nomination, but the black comedy has developed a cult following over the years.

By 2002, Williams had showcased his dramatic chops time and time again, but he had never inhabited a character quite as haunting as neighborhood photo technician Sy. Although he may seem harmless, Sy's lonely existence leads him to terrorize a family of regular customers, the Yorkins, by making separate copies of their most personal pictures and even confronting the family patriarch when he meets with his mistress.

Unlike many of his lead roles, the part of crime novelist Walter Finch in Christopher Nolan's psychological thriller about the murder of a teen in a sleepy Alaskan town was small, but vital. How vital? The comedy king was the — spoiler alert — killer, creepily brought to life by Williams.

Williams played Theodore Roosevelt in the Ben Stiller comedy and reprised the role for the 2009 sequel Night at the Museum: Battle of the Smithsonian and the upcoming Night at the Museum: Secret of the Tomb, which will be released Dec. 19.

Williams played another president — Dwight D. Eisenhower — whose administration hires Forest Whitaker's titular butler in 1957. He shared a SAG nomination for film ensemble with the rest of the cast.

Williams attempted to make a small screen comeback in this 2013 CBS sitcom created by acclaimed writer David E. Kelley (Ally McBeal). Williams let loose on a weekly basis as the eccentric but gifted advertising executive desperate to please his harried daughter and (sort of) boss, played by Buffy alum Sarah Michelle Gellar. CBS canceled the show after one season.