Because if you add another, the flimsy excuse to not do shit like that in the future is extinguished. You'll have crossovers as rampant in Hollywood as 'regurgitated old shit' is now. Not only that, but they'll be expected to continue sequels in this series with a new icon in each one, increasing the ridiculousness to the level of a Sailor Moon/Dragonball/Yugi-Oh fanfic.
Well, without the inclusion of 'manhood's and 'hot aching spot's.
Hybrid Mode
