On the Showtime series, now in its second season, Lewis plays Nicholas Brody, a former Marine sergeant who secretly converted to Islam while a prisoner in Iraq. Obama's religion has been the subject of conspiracy theories, but the president often speaks of his Christian faith.
Lewis admitted that he had misgivings about his joke, but that he had written it in indelible Sharpie ink.
“And I couldn’t take it back," he said. "I was then writing emails for the whole of the next week going: ‘I do hope he understands irony.”’
Lewis said his "Homeland" co-star Clare Danes wrote a much more "stylish" note on the DVDs, saying, "I was a fan of yours long before you were a fan of ours."
Obama has called Homeland his favorite show. Lewis said he asked the president when he finds time to watch the show, since he seems a little busy "running the free world.”
“'On Saturday afternoons,'" Obama explained, according to the actor. "Michelle, she takes the two girls, they go play tennis. I go into the Oval Office. I pretend I’m gonna work and I switch on 'Homeland.' ”
Entertainment Weekly has the video.