Street Fighter IV producer Yoshinori Ono had his "Street Fighter IV and Beyond" panel interrupted by Tekken producer Katsuhiro Harada, with the rival fighting game makers joining together to announce a collaboration, Street Fighter X Tekken.
Street Fighter X Tekken was introduced with a teaser trailer featuring Street Fighter's Ryu facing down Tekken's Jin in a pre-rendered sneak peek featuring Street Fighter IV's sketchy, inky visual style. The game, pronounced "Street Fighter cross Tekken" will be coming to the PlayStation 3 and Xbox 360.
Following the announcement, Ono surprised the crowd by holding up a Blu-ray disc with a copy of the game, then provided attendees with a live, playable demo.
Street Fighter X Tekken appears to feature Street Fighter IV's gameplay mechanics, locked onto a 2D plane, with both Tekken and Street Fighter characters performing EX-style super moves. The match started off with Ryu versus Kazuya Mishima, but Ono and Harada tagged in two more characters, Street Fighter's Chun-li and Tekken's Nina Williams. Ryu deployed his trademark fireball Ultra move, with Kazuya later following that up with his spinning electrified uppercut.
Harada followed that playable match with an announcement of his own, confirming that Tekken X Street Fighter is also in development at Namco. That game is rumored to play in the style of Tekken, with contestants fighting in a 3D arena.
Ono said the games won't be out "for a while" and that fighting game fans should enjoy Marvel vs. Capcom 3 while they wait.
Update: As some commenters have pointed it, Tekken's Kazuya Mishima was the fighter that appeared in the demo and trailer, not Jin Kazama. Apologies for the error.