That is a really neat game that I play every time I go to Vegas.  If you want to find online casinos with a similar game, go to http://www.ranked-online-casinos.com/igt-slots.html

There is a game at online casinos with Microgaming software called What on Earth.  It is very similar to the Little Green Men game in land-based casinos.  The site listed above has a list of casinos that have this game and offer great bonuses, promotions, and customer service.

Good luck and have fun!