That 'Game of Thrones' mistake reportedly gave Starbucks $2 billion in free advertising

Despite having one of the highest production values of any TV show in history, Game of Thrones is not entirely impervious to mistakes on-screen - something we all discovered from Sunday's episode. No, we're not talking about the fact that ** spoilers ** Daenerys couldn't see that huge fleet of ships heading towards her with dragon-slaying crossbows, but rather that neither the cast nor the editors of the show spotted a takeaway coffee cup sitting in front of Dany during the drunken celebrations at Winterfell.

If you didn't notice the mistake on Sunday's episode, here it is highlighted for you:

The mistake very quickly went viral on social media, with plenty of users seeing the funny side of the blunder.

Even the show's producers made a joke out of the mishap.

Needless to say, the error was very hurriedly fixed, and the coffee cup made its departure from the show as suddenly and as unexpectedly as Rhaegal. During its brief cameo, however, the cup managed to drum up a lot of publicity for Starbucks, where it was initially believed to have been from. In fact, according to NBC, that one little blunder gave the coffee chain an estimated $2.3 billion in free advertising.

Stacy Jones, the chief executive officer of marketing company Hollywood Branded, came up with the figure having analysed the number of mentions of "Starbucks" and "Game of Thrones" both on social media and on TV and Radio shows.

"This is a once-in-a-lifetime collision of opportunity for Starbucks," she said. "But really, this is just the tip of the iceberg, because what isn’t being monitored or estimated is the word of mouth and social media on top of this."

What's more, had this been a deliberate incident of product placement, it is believed that it would have cost Starbucks six figures to have their cup featured, simply because of how popular and influential the show is.

As for how the coffee cup got missed in the first place, it's difficult to say. Dozens of editors will have seen the episode before it was given the OK to be aired, and with a reported budget of $15million per episode this season, the audience are wondering how such a glaring error was left in.

Given how many times shots have to be recorded and re-recorded, it's possible that the coffee cup was only in the frame for one take - it just happened to be the take that was used in the final cut.

All in all, it's a pretty minor error, and HBO did a good job of covering it up ASAP. As for all the other complaints they've received about episode four, however, they might not be so easy to fix...