The video shows the stars struggling to grasp the concept of using reverse psychology to get young people into voting booths.
Required by director Spielberg to say "don't vote," Roberts remarks, "That doesn't make sense." Cruise and Smith complain to each other, while Timberlake jokes, "I can do anything. I was in a boy band, OK?"
Finally, Ford says, "You know what? I can't do it. It's not true, I don't believe it - 537 people decided the 2000 election, and you want me to tell people that one vote doesn't count?"
"There are more Baldwin brothers than that," quips Ryan Reynolds, whose wife Scarlett Johansson also appears in the video.
Also appearing: Cameron Diaz, Shia LaBeouf, Snoop Dogg, Neil Patrick Harris, Jason Segel, Zach Braff and Sacha Baron Cohen as his alter ego, Borat.
