I think Nisus was the app that had a fun About... window easter egg: if you did it with the option key down, little stick figures would assemble (or disassemble?) the dialog letter by letter, running back and forth frantically to do so.

Nisus also might be the Mac app that had the unusual scrollbars and basically no minimum size on the edit window.

You could make the window maybe 10 characters by 5 lines, and the arrows in the scrollbar would change to a smaller size.

Then smaller still and the scrollbar itself would get narrower.

Then smaller still and the arrows would change again, to simple triangles.

Then smaller again and the arrows would overlap and change to point right and left instead of up and down.

You could make the window so small only a single letter would display, then even a fraction of that letter.

Good times.