In season 9 of The Office, Dwight attempts to teach Erin the fictional language Dothraki. He does it so Erin can impress Andy Bernard’s educated family.
The joke appears in “Andy’s Ancestry,” the third episode of season 9, which originally aired on October 4, 2012. Dwight presents Dothraki as the language of the nomadic warrior horse lords of Essos, borrowing its fictional background from Game of Thrones.
Erin initially treats the lesson seriously, not realizing that Dothraki is fictional. Dwight’s exaggerated confidence makes the scene especially funny: he treats a television language as a serious social skill and later compares it with Klingon, another invented language from Star Trek. The episode also features Andy boasting about a supposedly distinguished family connection, which motivates Erin’s attempt to fit in with his relatives. The answer is sometimes confused with Klingon because Dwight mentions both, but Dothraki is the language he specifically teaches Erin.