The article focuses on two fictional languages – High Valyrian and Klingon. Learning them leads to various problems, mostly due to the fact that they are not officially spoken languages, and in practice are used only in the films for which they were created: Game of Thrones and House of the Dragon ( High Valyrian) and Star Trek (Klingon). For this reason, the learning resources are limited due to their specifics; neither are there specialists to teach them. In addition, unlike most spoken languages, neither a level of proficiency can be determined nor any formal certification can be issued for High Valyrian and Klingon. Although there are literary sources which deal with the two languages separately, mostly from the point of view of their lexical and grammatical characteristics, there are yet to be found publications in which the learning of these languages by real users is researched. The paper presents an analysis of the two languages from the point of view of linguodidactology and empruntology. A survey among users who learn the two languages on the Duolingo language learning platform and through other sources is provided. We reach the conclusion that using Duolingo to learn High Valyrian and Klingon leads to efficiency, but not to a 100% proficiency; therefore, additional sources and resources shall be consulted.