Okay... just brainstorming here:
Variation on the game where you can't say "baby" or you lose your diaper pin to the person who catches you... one with the most diapers at some predetermined time wins. Most showers I have been at lately have added "cute" and one or two other words to teh list because people got so good at not saying baby. So, get crafty and and instead of just basic safety pins use either pins or clothespins (some people get cranky about putting holes in their clothes!) and decorate them with a small bead sporting a ribbon tail. Egg and maybe sperm to the list of words you can't say.
Pin the Sperm on the Ovum... need I explain? If you tear or in any way damage your sperm you lose automatically.
If you do the game where you bring out a tray of items that people have to memorize and then list, do basic baby stuff but add theme items. a colored Easter egg, a turkey baster, test tube... I dunno what all. Ask your friends for input, or others who have gone that route.
If I think of more I will post again. Good luck and have fun. Ask your friends if there is anything in particular they are picturing.
Maybe cupcakes decorated like eggs with cute little smiling sperm diving into the middle.