Such as: missing a pop culture reference or incorrectly responding to an inside joke oblivious to the fact that it was an inside joke.
Origin: A "Who Wants to be a Millionaire" question asking to finish the phrase "Snug as a..." in which "mug from doug" was a wrong answer so absurd you'd have to be completely oblivious to choose it.
>> "are you listening to eminem?!"
> "uhhh, mug from doug."
> "We're going to Mongolian BBQ"
>> "The restaurant or the BBQ?"
> "what?! mug from doug."
> "A Volvo is faster because it is heavier and therefore has more inertia."
>> "mug from doug."