Making a TV show like Game of Thrones must be stressful. At the end of a long day, you just want to get that last shot of Daenerys and head home.
So maybe it's understandable that someone left a Starbucks or other modern coffee cup in a shot in last night's Game of Thrones? Although, this is the biggest show on TV, so you would think they have people whose only job is to catch stuff like this.
Either way, Twitter is having fun with it!