The EM-50 Listening Device is a 'bug' used by the NSA and, in particular, Casey to monitor Chuck in the Buy More. It features most prominently in "Chuck Versus the Marlin", when it is revealed as Casey's 'bug of choice'. It is similar to, but less advanced than, the GLG-20 Listening Device. Trivia: The EM-50 was the name of the Urban Assault Vehicle from the 1980 movie Stripes.