Some stand in the rain in Leicester Square, others camp outside hotels. But fandom goes to the next level when, as with a recent Game of Thrones episode, you can spot a Monty Python quote translated into a fantastical invented language.

In the episode Breaker of Chains, the show's linguist David Peterson created the ultimate in-joke with series creator Dan Weiss, by translating Monty Python quotes into Low Valyrian, a language used by a clan on the show. More specifically, he took the insults hurled by a French soldier in the movie Monty Python and the Holy Grail, such as "Your mother was a hamster, and your father smelled of elderberries."

"That was [series creator] Dan Weiss's idea and it was so hilarious that I had to do it," said Peterson in an interview on the production blog for the show. "There's a scene where the Meereenese rider is challenging Daenerys' champion. He's shouting and Nathalie Emmanuel [Missandei] is translating – but she's not translating what he's saying. He's actually saying a Low Valyrian translation of the French guy's insults in Monty Python And The Holy Grail." Nevertheless, sharp-eared fans noticed and managed to at least partially translate the Monty Python quotes the rider is actually shouting. "Right after that episode aired, I was getting tweets like: Is he saying a 'your momma' joke? Close… But no, he's actually starting out with, 'Your mother is a hamster.'"

Peterson has created over 5000 words for the three languages on the show, Low Valyrian, High Valyrian and Dothraki. The Monty Python reference is not the only secret message that Peterson has embedded in the show, but others are rather more romantic. "My wife has a word in every language [in the show]" he says. "Her name is Erin, which is the basis for 'kind' in Dothraki. My cat's name is Keli and the word for 'cat' in High Valyrian is 'kēli'." His favourite word meanwhile is from the "shamelessly pretty" High Valyrian language: Zaldrizes, meaning dragon.