Because global migration and mobility have increasingly blurred boundaries, questions of authenticity have become more complex than ever, and the issue of what constitutes "real" versus "fake" language practices and language users has become increasingly important. The newly emerging images of imposters associated with bilingualism and transnationalism have put bilingual and multilingual language users in a fragile position, where bilingual displays can summon the damaging image of inauthentic bilingualism and frame them as imposters who try to articulate their alleged modernity by mimicking other "reals." Focusing on the issue of authenticity, this ethnographic study explores how Korean-English bilinguals navigate and respond to the newly emerging images of imposters associated with bilingualism and transnationalism. In particular, I examine the case of 20 South Korean graduate students in the USA who have both advanced English language proficiency and native Korean language proficiency. Because they are in a relatively advantageous position in being able to flexibly use both the Korean and English languages and to employ a variety of linguistic resources, their bilingual practices and performance provide an excellent example of the ways in which bilingual language users locate their social positioning through the selective production of ideological representations or language registers associated with images of inauthentic bilingualism. The findings highlight the agentive role of bilingual and multilingual language users in participating in the reconfiguration of what counts as legitimate bilingual competence and performance, and in making a very calculative investment in distancing themselves from particular types of language registers, language competences, and models of personhoods associated with inauthentic Korean-English bilinguals. These findings present a challenge to traditional research in the fields of second language studies, and applied linguistics, and urges researchers to look at the actual language practice of bilingual users who actively participate in the process of developing sense-making discourses. [ABSTRACT FROM AUTHOR]