Thousands of Doctor Who fans have complained about a cartoon that appeared at the bottom of the screen at the end of Saturday night's episode.
The animated version of TV host Graham Norton popped up at a really exciting moment, and almost covered actor Matt Smith's mouth while he was talking.
The cartoon was a trailer advertising the next show, Over the Rainbow, hosted by Graham Norton.
The BBC said: "We apologise for the timing of Saturday night's trail."
Lots more people have written about the incident online, saying it ruined the episode.
It's not the first time Norton has angered Doctor Who fans.
In 2005, his voice was heard for a few seconds at the beginning of an episode, because of a technical mistake.