Shift+click the green flag (or don't, if you want to see what's going on). Yet another pi calculator [sorta]. Pi is an irrational number, so it cannot be perfectly expressed as a fraction (i.e. 13/4 22/7, etc.), but we can get some pretty close estimates. This program finds each such fraction that can estimate pi, starting from 1/1. 355/113 in particular expresses pi very well while still being easy to remember.
Due to Scratch's limitations with dividing you can only get to about 6 digits of accuracy here. If you look inside, you can see some of my failed attempts to get past this limitation. Ideas are welcome. :)