Inglourious Basterds (Quentin Tarantino, 2009). In the bar scene, British officer Archie Hicox poses as a Nazi. His cover collapses when he orders three drinks using his index, middle, and ring fingers, a distinctly British gesture. 

Blade Runner (Ridley Scott, 1982). In the Voight-Kampff scene, Deckard tests Rachael, who poses as human. Her cover slips through overly controlled responses, revealing her as a replicant.

The West Wing (Aaron Sorkin/NBC, 2000). In the “Shibboleth” episode, President Bartlet tests a Chinese refugee claiming Christian faith. The man reframes the test itself, arguing that true belief cannot be proven by signs.

 My Fair Lady (George Cukor, 1964). In the embassy ball scene, Eliza Doolittle, after being trained by Professor Higgins, poses as a duchess. Through flawless pronunciation and refined manners, she passes completely, showing accent as a shibboleth of class.