"What's growing up in my garden?"

That's the question that popped in my mind when I walked outside my door last Thursday morning and noticed that three big white tubes (to give you an idea, the biggest was about 10 cm high, and the shortest, 4 cm) appeared suddenly in the lawn. They looked naughty.
I didn't give a lot of importance to the little tubes during the day, until I came back to my house and saw them once again. They looked exactly the same as they were that morning, but still, they were an enigma to me.
By then, many hypotheses started to arise in my head: "Are those some kind of cocoons? Or maybe somebody just planted those things there and they aren't even real? What possibilities are there that it is actually a spider-nest? (Because, by the way, I have nightmares with spiders)".
I could have made thousand of theories, all false perhaps. The only truth I knew is that they were something that I never saw before, and therefore, I wouldn't even touch them and I'd only wait and see what happens.
The next day (Friday, this means, today), I went out very early to the garden to see what happened with the mysterious tubes. Unfortunately, it was quite dark, but I noticed that something happened to them. They didn't look the same than the last day. However, I decided that it'd be better to examine them as soon as I'd be back from the things I was supposed to do. And I did so, slightly afternoon, I was back to discover one of the most amazing things I've ever seen: the tubes became mushrooms! and big ones! I wonder how can mushrooms grow up so fast: On tuesday night, there was nothing in the garden... by thursday, those big tubes appeared, and by friday, they were fully grown mushrooms.
What kind of mushroom are those that I found outside? After doing some research, I found out that their scientific name is Coprinus Comatus, but they're commonly referred as "Shaggy Inkcap" (its actual picture is on the right), a sort of fungus that commonly grow in lawns especially during the summer and fall, and which are found across North America (hum, now it makes sense!); some of these mushrooms have been found reportedly in Australia and New Zealand recently. They are indeed edible when they're in their youngest stages, but not when they start leaking the black ink from its cap (hence the name, ink cap).
However, although I found some information about them, I still can't explain to myself how did those mushrooms appeared precisely in my garden. But it was amazing to see them grow there: it's the first time that I see an organism grow so fast until maturity! And best of all: They aren't poisonous.
So, if you find some strange white tubes in your garden any of these days (especially if you live in North America), keep an eye on them: they could be Shaggy Inkcaps as well!