Kurt Russell was worried that Tombstone would get buried at the box office by the more expensive Wyatt Earp, but Tombstone ended up outgrossing its competitor by a pretty huge margin. Since movie development can take years and years, it’s not uncommon for rival Hollywood studios to put two eerily similar films into production at the same time. The phenomenon is called “twin movies,” and it happened with Volcano and Dante’s Peak, Armageddon and Deep Impact, and No Strings Attached and Friends with Benefits.