Cersei is meant to be the child of Tywin and Joanna Lannister - but Kristian's clanger suggested Mad King Aerys is in fact the real dad. That would also mean that her twin Jaime Lanister is a secret Targaryen.
It could have been a slip of the tongue or simply a factual blunder, but the error sent fans reeling on Twitter, immediately speculating about the situation.
Someone took matters into their own hands and tweeted the actor himself, asking if he simply got confused, to which he appeared to get flustered and reply: "I just said the wrong name".
However, many fans have questioned whether or not Tyrion is secretly a Targaryen, making him sister to Mother Of Dragons Daenerys.
One of the plot points that sparked this theory was when the Lannisters' mother Joanna hinted that she was once a lover of the Mad King.
Parentage has been an issue on the TV series, with Jon Snow being confirmed at the end of season six to be Rhaegar Targaryen's son by Lyanna Stark.
Things are gearing up to a major battle on the show, led by Daenerys and her dragons, which has always meant to "have three heads".
Could Tyrion be the "third head"? And if so, does this mean he'll be switching sides to fight his brother and sister? Or is Cersei the one switching sides, as suggested by Kristian's blunder?
Or, will battle commence between the two sides, only for the Lannisters to discover they're immune to dragons, thanks to their bloodline, consequently rendering them nearly invincible against Jon and Daenerys?
*Game of Thrones airs on SoHo on Mondays at 1pm and 8.30pm and is available on NEON.
