"I'm not sure Robin had completed doing his voice in the movie. He was doing the voice of my dog and I hope that he had completed it because it would be a real shame not to have him in it. And of course there will be a degree of sadness there, but the work he did do would have been done with his usual verve and brilliance," said Pegg.
Lionsgate UK declined to comment on whether Williams' contribution would be included in the final cut.
In the film, a sci-fi comedy featuring members of the Monty Python team, is said to follow a schoolteacher (Pegg), who is given the incredible power to make his every wish a reality by a group of aliens (voiced by the Pythons). The Terry Jones-directed film does not have a release date yet.
UPDATE: Producers Bill Jones and Ben Timlett released the following statement saying that Williams did indeed complete his work.
"Contrary to reports, we are able to confirm that Robin Williams completed his voice work recording for the role of Dennis. Everyone on the 'Absolutely Anything' team was distraught to hear the sad news and we send our condolences to Robin's family."