Computers were used to create so many illusions in Forrest Gump, from removing actor Gary Sinise’s legs to having Tom Hanks interact with JFK and John Lennon, that viewers may have not even noticed one of the film’s more sneakily brilliant tricks. Specifically, there is a memorable passage in the movie during which the title character’s considerable ping-pong skills make him famous during his stint in the Army. He even serves as an ambassador of sorts for his home country when he is invited to play ping-pong behind the so-called Bamboo Curtain, becoming one of “the first Americans to visit the land of China in, like, a million years.” Arbitrary as this plot twist may seem, “ping-pong diplomacy” was a very real part of Richard Nixon’s plan to establish detente with China. But how, exactly, did Tom Hanks manage to play table tennis so convincingly in the 1994 Robert Zemeckis smash? A behind-the-scenes DVD supplement has some answers.

Hanks had some ping pong prowess, no doubt, but his skills were not up to those of his character, so some digital deception was employed. The actor and his opponent, billed only as Valentine, are simply swatting at the air with their paddles, timing their action to the sound of clicks. The ball was added optically later. For Hanks, this kind of pantomime came naturally, but his scene partner was a genuine ping-pong wizard who had to adjust to playing his favorite sport without a ball. Though it goes unmentioned, this brief documentary also demonstrates how Zemeckis’ film deftly employs digital background extras. In the finished film, Forrest seems to be playing-ping pong in a packed stadium with many spectators. In reality, the game was shot on a soundstage with relatively few actors on hand. As Zemeckis puts it: “Movie magic.”