TV
Y'know, raiding an Englishman's fridge is like dating a nun. You're never going to get the good stuff.
— Whistler ‧ Buffy the Vampire Slayer

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The comparison links a disappointing search for food with a deliberately provocative image of romantic frustration. In both cases, the speaker claims that the desired reward will be unavailable. National and religious stereotypes do the work of the joke, rather than any serious explanation.
Context reviewed