It has been a topic in psychiatry, it is referred to by translingual writers, and bilinguals report it frequently -- the feeling of becoming a different person when using a different language. The present study was set out to investigate the reasons behind this feeling. We looked at the effects of biculturalism and personality traits, as well as introspective data from 88 German-English bilinguals. The analyses revealed no significant effects of biculturalism. However, an effect was found between high levels of Agreeableness and an affirmative answer to the feeling of a changed self. Furthermore, an integrated approach suggests that four main categories play a vital role in giving rise to this feeling, namely cultural differences, language proficiency, 'breaking free' from the L1 personality, and changes in personality due to reactions of interlocutors.