I’m often a little perplexed by viral marketing efforts that put your friend’s photo into the scene, or call your friend on the phone or something like that. First of all, half of them can be really threatening—the ones for Funny Games last spring let you watch your friend be tortured. And when you put your friend’s still photo on a moving body in the video, the effect can be really weird and forced.

Both of those problems are avoided with the neat video for Step Brothers, which is waiting for you to customize at a site called Step Brothers Duel. Will Ferrell and John C. Reilly, not in character but still squabbling like siblings, get in an argument over their friend, who turns out to be whoever you suggest. I tried using George W. Bush the first time, just because it was fun to see Will Ferrell moon over a guy who looks so much like him.

You also have the option of having them call your friend, but if you’d rather they just be amused than harassed by two actors, just stick with the video. And hope they’ll return the favor, because, come on, you know you want to see Will Ferrell hold up your photo and call you his best friend.