This game was created in front of a live audience, on the September 22nd meeting, as a demonstration of some of the basics of Game Maker. You can see a teeny bit more about the game in this blog post.
Controls, if I recall correctly:
S: Left player
Right player: ↑
Space : Restart
(I do not necessarily recall correctly.)
Source code, in the form of a .gmk file, is included with the download; you can open and modify it with version 8 or higher of Game Maker.
The idea for the leprechauns
Some other people (let me know if you remember who):
The ideas for the bunny and the bats