I've only seen one so far. I read stuffon a page called SCP wiki, it's usually short sci-fi/horror stories, some brilliant some not so good. Today SCP has become super cute pets, I though that was a pretty good one.
Lol, I jest. I've seen lots of little ones like "This Japanese Historian has found an old karate manual by such 'n such a chap!" which of course turned out to be bogus and the guy's name supposedly was "April" and "Fool" in Japanese - and a video of some guys wrapping their friends' entire car in tin foil, but that's about it.
That kind of thing has been done umpteen times by them and us. I remember once was back when KickChick was Admin and I think Bullshido used our shades of blue and threatened to moderate the site. Others that have been done include the MAP Dating Site (Web Archive capture for proof) and (this one turned rather ironic) slipthejab, back when he was just a pain in the rear for the mods, being promoted to Global Mod. The irony? He eventually did become a moderator.
Oh I've trolled Bullshido before, but I went solo last time. And it was glorious, and thoroughly entertaining. I have a prank in mind already since I was too preoccupied to organize one last year and this is a good week for me to get one started. It'll hafta be organized off MAP though as I don't have the inbox space to do so within MAP, and they'll obviously check our site once someone goes too outlandish with the prank and it's clearly a collective effort. I can say no more about this for operational security reasons. *poof* (American version.)