Mushroom Battle mode is one of the highlights exclusive to Tekken Tag Tournament 2 Wii U Edition. This adds Mario themed items like Super Mushrooms that make fighters grow, Poison Mushrooms that shrink and damage characters, and Super Stars that grant temporary invincibility. I played Mushroom Battle mode and it has more of a "party game" kind of feel than standard Tekken.
Producer Katsuhiro Harada explained while you typically get stronger when you eat a mushroom, growing changes the distance and range of your attacks.
Originally, the "mushroom battle" mode didn’t have a Nintendo theme. The Tekken team was playing with the concept of character scale while developing Tekken Tag Tournament 2.
"When we were developing the game early on, we had this new feature where you could scale the character size making them bigger or smaller," Harada explained. "We were playing around with that. It was interesting and entertaining, but we didn’t really have any good ideas to tie that to gameplay. When the Wii U version came along we thought it’s Mario and it makes sense if you’re Mario to eat a mushroom and get bigger."
"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," Harada disclosed. "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."
Not all of the Tekken team’s ideas were Nintendo material, though. "We would like to try some violent features like raising poison mushrooms below the stage and then you can take them online and when you’re fighting your friend you can shove it in their face," Harada joked. "We’d like to try some violent features like that, but I don’t like Nintendo would agree with that. I think they would be kind of angry!"
Tekken Tag Tournament 2 Wii U Edition also has a number of Nintendo themed costumes. These ideas came from the Nintendo side where they asked the Tekken team if they could give one of their fighters a certain Nintendo costume.
Regarding characters, Harada prefers not to have platform exclusive characters like the Soulcalibur series. That doesn’t mean there is a zero percent chance Tekken or another fighting game series will get exclusive characters, though. "We are a third party developer, so there might be some instances where a first party says the game will be much more exciting and we can hype it more if this particular character is in it. That was probably the case with some of the other titles we made."