Baby shower fails and successes?

I am planning a baby shower for my friend and we are expecting about 50-100 co-ed people. We already have a place picked out and now all the details need to be planned.

Please comment if you have any stories that you would like to share about a baby shower that you attended or hosted where things went wrong and how you think the "fails" could have been prevented or avoided. Post any definite no, nos!

To add to that, if anyone has any success stories about baby showers that they have been to, please share what made them great. I still need great game, food, and center piece ideas for a large group. Post any must have's!

The theme is underwater and we would like to have as many cheap and environmentally friendly things as possible.