Tekken producer says that Nintendo was very cooperative and understanding with them
This comes from Tekken Tag Tournament Two (TTTT) producer Katsuhiro Harada:
“That was an an idea from our side that they approved. We also told them we wanted to use the stars for invincibility and they were OK with that. We do use some of the sound effects from Mario and remix some of the music. Some of these are things we really wanted to do, but we thought Nintendo would not be OK with. They actually were and they made it into the game as you can see. They were very cooperative. We didn’t expect to get as far as we did. There aren’t many third party games that go as far with Nintendo properties so you can see how understanding they were this time.”
Sounds like Nintendo might be opening up to a few more developers in the same way that they have with people like Capcom in the past. Though, I doubt that Namco Bandai will be developing any Zelda games anytime soon…
