Now, actress Emilia Clarke, who played Daenerys Targaryen and was among the main suspects, has blown the whistle on the co-star who was actually responsible for the error.
Eagle-eyed fans of the hit fantasy epic were quick to spot the rogue disposable cup among horns and goblets of booze during a scene in which the survivors of Winterfell celebrated defeating the Night King.
During an appearance on Jimmy Fallon’s US talk show, British star Clarke revealed it was co-star Conleth Hill, who portrayed Master of Spies Lord Varys, saying he admitted to being responsible for the error during a pre-awards show party in September.
“We had a party before the Emmys recently and Conleth, who plays Varys, whose sitting next to me in that scene, he pulls me aside and he’s like, ‘Emilia, I have got to tell you something, love. The coffee cup was mine’.”
Obviously a serious allegation – and Fallon pressed the actress on whether she was sure it was Hill.
It appeared during episode four of the show’s eighth and final season in May, but was later removed from re-runs.
And it was not the only anachronism of the final series, with a plastic water bottle spotted in a key scene of the last ever episode.
The final series of Game Of Thrones, which aired earlier in 2019, drew heated debate from fans and critics as to whether it provided a fitting ending.
A petition calling on the writers to remake the season has attracted more than 1.7 million names.
In interviews, Clarke has defended the ending, saying the stars knew they could not please everyone.
“Where I think we got with the show is as good an answer as there could be,” she told Variety earlier this year.