I've bought the organic cucumber and is it an icon or other item?

It's a collectors item, it literally does nothing other than sit in your inventory.

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I see it as a way to show other people that you have a f*ckload of tc. And that you are willing to spend 10k on an item that literally does nothing.

Well, it's items for rich people who have nothing else to buy. There is also an achievement for owning 100.

Oh.... Ok, but now, I have another question about items too:

What does the world championship 2008 (and the others) do?

They were entry tickets to the 2008 and 2009 world championship.

Nowadays they are just collector's items.

Ah ok. Thanks.