Obama, who took a quick pop culture quiz during an appearance Tuesday on ABC's "The View," drew a blank when asked to name "the controversial sex book that's on millions of women's bedside tables."
"I'll ask Michelle when I get home," he promised, to hoots of laughter from the audience.
Obama did better with TV and celebrity trivia.
He knew which Kardashian was married for just 72 days.
"That would be Kim," he answered, saying he only knew because she was married to pro basketball player Kris Humphries.
He's seen "The Avengers," and was able to name three superheroes: Hulk, Captain America and Ironman.
And he knew that View participant Sherri Shepard had been on "Dancing with the Stars."
He didn't know whether Jessica Simpson had had her baby. (She had a girl earlier this month.)
Obama said he catches up with TV shows like "Mad Men" and "Homeland" on long flights such as trips to Afghanistan, when there's time to study his briefing books and still have hours left over.
And he said his daughters, at a private 50th birthday roast for their dad, gave him credit for being embarrassing, but "not too embarrassing."