The Cairo Declaration - an upcoming war film produced by a company affiliated with China's military - is part of a host of government-directed events to commemorate the 70th anniversary of Japan's surrender.
The US, Britain and China met in Cairo in November 1943 to map out a post-war path for Asia, during which they decided that territories ceded to Japan before the war should be returned to China.
China - then known as the Republic of China - was instead represented by Nationalist leader Chiang Kai-shek, who went on to lose China's civil war to Mao's Communist forces.
"I'm sad that my contributions at the Cairo Conference haven't been recognised in the film," joked one user today.
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Others were more jaded.
"Let Mao be a part of the conference, it's not like the rest of our history is real anyway," wrote another user.
A trailer for the film posted on YouTube opens with Mao making an impassioned speech saying, "The task for Communists around the world is to oppose Fascism through struggle".
The poster advertising the movie features the actor playing Mao looking out into the distance, but a website has been set up allowing Internet users to mockingly edit themselves or others in his place.
Edited versions circulating on social media variously had in Mao's place Gollum, the fictional character from The Lord of the Rings, as well as a Minion, the yellow workers from the Despicable Me film franchise.
"By featuring Mao, who was not present at the meeting, but excluding Chiang, the poster shows no respect for history nor to Mao," culture critic Sima Pingbang was quoted as saying by the Global Times tabloid.
An editorial in the Chinese-language edition today of the newspaper, which has close ties to the Communist Party, called the use of Mao to promote the film "inappropriate".