Props and sets from the Wallace and Gromit films have been destroyed in a warehouse blaze.
The warehouse contained Aardman Animations' archive
The storage building belonging to Oscar-winning Aardman Animations, contained the company's "entire history", a spokesman said.
Wallace and Gromit creator Nick Park said it was "dreadful" for the company but comparatively "not a big deal".
The Curse of the Were-Rabbit, the new Wallace and Gromit film, has just gone to the top of the US box office chart.
Company Spokesman Arthur Sheriff said: "It couldn't have come on a worse day - we were supposed to be celebrating, but instead our history has disappeared in a couple of hours.
"Everything has gone, from as far back as Morph and all the way through to Chicken Run, including Wallace and Gromit, Creature Comforts, it's all there. Everyone is devastated."
Aardman co-founder Dave Sproxton said one of the most important losses was a complete exhibition of the three Wallace and Gromit short films which was recently brought back to the UK after a tour of Japan.
Mr Sproxton said: "A lot of the original sets were there, including several panels of original storyboards and that, in a way, is the biggest loss. It's basically a ready-to-go exhibition and sadly that's been destroyed."
He added that the films themselves were stored elsewhere and so had not been damaged.
Mr Park, who won Oscars for animations such as The Wrong Trousers and A Close Shave, said: "Even though it's precious stuff and nostalgic - and it's dreadful news for the company, in the light of other tragedies it's not a big deal."
Fire crews were called to the building near the city's Temple Meads station at about 0600 BST on Monday. They were unable to stop all three floors inside collapsing.
Creator Nick Park said the fire was "dreadful" news
Avon Fire Service divisional officer Geoff Cater said: "All three floors inside have collapsed and the exterior walls are unstable.
"We couldn't commit people inside, so we are fighting the fire from the outside which is more time consuming."
At the height of the blaze, flames were reaching 100ft, he added. Nobody was in the building when the fire broke out.
The area has been sealed off and crews are expected to remain at the scene for the rest of the day.
Aardman Animations was set up by Peter Lord and David Sproxton in Bristol in 1976. A year later, the duo created claymation character Morph.
The company has gone on to produce everything from pop videos to adverts, short films to feature-length movies.
Nick Park joined the firm in 1985, winning his first Oscar five years later for the Creature Comforts animations, which beat Wallace and Gromit offering A Grand Day Out to the prize.