REIMU: I hope you're not saying that freezing them released more life-force.
MARISA: No.
AYA: So, was there enough life-force for one mushroom to become a youkai, but the presence of the others sort of "distracted" it ...?
ALICE: Sort of. Living things generate their own life-force, occasionally to the point that it produces a youkai from an object.
NITORI: Yeah! But in this case, each mushroom only had enough life-force surrounding it for its own stuff. When Cirno removed most of 'em, the remaining mushroom had enough to become a youkai.
REIMU: Moreover, the energy was already busy unleashing the spores -- I believe the "spirits" were actually little clumps of life-force that were floating along with the spores, and they became mindless ghosts upon contact with a living host -- which is to say, us.
AYA: Aha! So when you and Shinki put up a barrier that wiped out the spirits or whatever, the energy was now free to produce a youkai!
MARISA: And I would've got away with it, too, if it hadn't been for you meddling kids and that stupid dog!
.....
REIMU: ...What?
AYA: What?
MARISA: Uh, never mind.
NITORI: Hang on ... mushrooms aren't really individual life forms, they're each just one extension of the mycelia underground.
MARISA: Duh, she's a mushroom youkai, not a mycelium youkai!
AYA: And I didn't have it exactly backwards ...
MARISA: Shaddap, it makes sense!
REIMU: Hah. Well, insofar as we haven't actually met this Masha Kinoko yet, we seem to have resolved this Incident more cleanly than certain others ...
MARISA: Yeah, I guess. Now what?
REIMU: Up to you. You're the one who figured it out first.
Eletale
haha, all this party thing made me remember this
http://www.youtube.com/watch?v=pFmvFA_cKAE