Earlier studies in physics education research have shown the importance of analysing students' processes of ‘becoming a physicist' in a wider sense. For example, it is often expected of physicists to have a kind of ‘authentic intelligence' or ‘smartness', which is generally perceived as male. In this study we contribute to this area of research by analysing an area often forgotten in educational research: humour. Empirically, this study is based on 177 jokes from physics lectures, collected from three different higher education contexts, the US and two Scandinavian countries. With a discourse analytical framework we explore the question of how teacher's jokes in physics lectures portray physics and physicists. In the analysis of the teacher's jokes, physics is constantly constructed as difficult and very advanced, mainly through ironically speaking of it as ‘easy'. Physicists are portrayed as single minded and very passionate, not to say obsessed, about physics. In this study we argue that although none of the jokes were mean the jokes contributed to a discourse that can be perceived as problematic in limiting the conceptions of who a physicist may be.