The GLG-20 Listening Device is one of the most advanced listening devices currently in service with the US, and is in limited use by both the NSA and CIA. In "Chuck Versus the Marlin", Chuck finds an example hidden in a Buy More sales rack, and hands it over to Casey, believing Casey is spying on him. Upon inspecting it, Casey realises it is a GLG-20, and he only uses the less advanced EM-50s, meaning it must have been placed by an outside source. A total of 30 examples are found by NSA clean-up teams, hidden around the Buy More. These were then confirmed to have been placed by Fulcrum agents, revealing that Fulcrum now has access to the GLG-20. The EM-50 Listening Device is similar, and in more widespread use, but less advanced.
In "Chuck Versus the Marlin", it is claimed that the device uses a "high powered transmitter to avoid detection", and has "a maximum range of about 20 yards".
- The GLG-20 is a reference to the movie Spies Like Us (1985). Chevy Chase and Dan Akroyd portrayed two bumbling government employees who are recruited by the CIA to serve as decoys and GLG-20 is the rank they receive upon graduating from "spy school".
- The EM-50 is a reference to the movie Stripes (1981). Bill Murray and Harold Ramis play newly minted GIs who end up driving the EM-50 Urban Assault Vehicle from Italy to West Germany to visit their girlfriends. However, they wind up rescuing their unit in Czechoslovakia after taking a wrong turn attempting to retrieve the EM-50 from Murray's and Ramis's characters.