Dave Kap's memoir of going from Second Life user to Linden Lab developer last week included this passage:

"I think invisiprims were the first major example of that — it's a texture hack that almost got removed until it was realized people were using it to make better custom characters." For instance, see below. "This was before animations let you fold your character into itself. So thanks to residents, the ‘bug’ of invisiprims never got ‘fixed’.

“So basically," Dave tells me, "what it comes down to is: Pick any positively-received feature you want from the entire development of Second Life and I guarantee that some part of it was shaped by how residents reacted to it.”

And that's why, say, Iris Ophelia's tribute to the machine gun leg from Robert Rodriguez's Grindhouse was possible:

First image via Darien Caldwell 's fun tribute to the history of the SL shoe industry.