It is Hollywood's cruelest trick, that the recorded images of an actor, and the characters they have inhabited, live on long after death. Robin Williams, the 63-year-old film and television star, who died at his home in Tiburon, California, this week, leaves behind three unreleased films.

In the coming year, those films - November's A Merry Friggin’ Christmas, December's Night at the Museum: Secret of the Tomb, and 2015's Absolutely Anything - will be released, and audiences will get a parting glimpse of the final work of a comedy icon.

A fourth film, Boulevard, which premiered at the Tribeca Film Festival in April, is expected to hit cinemas later this year as well.

The three as-yet-unseen films are largely intact, unlike Heath Ledger's final film The Imaginarium of Dr Parnassus, or Brandon Lee's final film The Crow, which were only partially completed when those actors died.

In some cases, when an actor dies before production is finished on a film, digital imaging is used to replace them, one notable example being Oliver Reed, who died before filming on Gladiator was completed. And in others, such as Marilyn Monroe's final film, Something's Got to Give, production is simply abandoned. In River Phoenix's final film, Interview with a Vampire, his role was re-cast, with Christian Slater.

The first of Williams unreleased films, A Merry Friggin’ Christmas, is a holiday-themed film about a father (Joel McHale) who realises he has left behind his son's Christmas presents while on holiday with his family. In the film, McHale's character and his own father (Williams) return home to retrieve the gifts.

The second is a sequel to Night at the MuseumSecret of the Tomb, which stars Ben Stiller, Rebel Wilson, Ben Kingsley, Dan Stevens, Owen Wilson and Ricky Gervais. In it, Williams reprises his role as Theodore Roosevelt.

The third is a British science fiction comedy; Absolutely Anything. Though not strictly a Monty Python film, it was written and directed by Terry Jones and stars Jones, Michael Palin, Terry Gilliam and John Cleese. In it, Williams voices Dennis the Dog, the animated sidekick of the film's lead, Neil (Simon Pegg).

A fourth film, Boulevard, has already been released at the Tribeca Film Festival, but is not yet in wide release. It is perhaps the most complex piece of work Williams leaves behind. In it, he plays a middle-aged, married man who explores his homosexuality and forms an unlikely friendship with a male prostitute, played by Roberto Aguire.

"This is one of the kindest characters Williams has ever played, which makes his self-imposed turmoil — the consequence of not wanting to hurt anyone, least of all his wife — all the more tragic," Variety critic Peter Debruge wrote after the film premiered in April.

"Tapping into that same loneliness felt in One Hour Photo and Good Will Hunting, the actor projects a regret so deep and identifiable, viewers should have no trouble connecting it to whatever is missing in their own lives — whether those regrets are romantic, sexual, professional or spiritual."

The footnote to Williams' body of cinematic work is not what we know, but what might have been.

Williams was planning to return to the role of Mrs Doubtfire, the Mary Poppins-esque nanny he made famous in the 1993 film about an estranged father who who concocts the character to return to his family in disguise and win back their love.

The sequel, Mrs Doubtfire 2, was in development at 20th Century Fox, with Williams and director Christopher Columbus (who directed the original film) on board and a second draft of the script in play from screenwriter David Berenbaum.

Plans for that film are now uncertain. Some US media outlets are reporting Fox might re-cast the role, but that seems unlikely. If Williams did anything in a career spanning four decades it was demonstrate time and time again that he was one of a kind.

* In the US, A Merry Friggin’ Christmas opens on November 7, Night at the Museum: Secret of the Tomb opens on December 19 and Absolutely Anything is scheduled for 2015. Boulevard was screened at the Tribeca Film Festival but does not yet have a distributor for general release. In Australia, Night at the Museum: Secret of the Tomb opens on December 26; A Merry Friggin’ Christmas, Absolutely Anything and Boulevard have not yet announced Australian release dates.