Not having seen the demo of John's "StarLogoWorld", I could be very
wrong. But my impression is that you can play around with multiple
turtles in Squeak with no additional code. Smalltalk-80 had a subclass
of Pen called Commander (or was this only a Smalltalk V feature?) which
allows you to things like:

> Then we wrote some Smalltalk to place all the turtles in one spot,
> and then told them to move forward in a random starting direction.
> This created a circle. 
> 
> Then we lined them up and had them go forward a random amount and got
> a growing halo type of image.

It is not StartLogo, of course, and not even enough to:

> Although you are dealing with thousands of turtles you can do neat
> things. For example we can have the turtles leave scent trails, then
> we can have the turtles hunt for the best scent intensity. For that
> example you get clumps of turtles, with turtles occasionally peeling
> off and going to another scent clump.

Actually, with a lot of imagination it might even be possible to do
something like this with the standard classes...

On a related subject, I once designed a language called NeoLogo (see
http://www.merlintec.com/pegasus2000/e_neologo.html) and partly
implemented it in Self. I was going to implement it in Squeak as well
so more people who try it out, but never got around to it.

-- Jecel