I call this the Bizarre "B" Special: that's Baby Bigfoot on a BBQ, surrounded by beer bottles and a bonsai tree. Feel free to personalize your own creation, though, and have fun with it! How about an Irish infant in an igloo, surrounded by indigo ibexes?
Forget safe, traditional pastels; you want to "go" for as many subtle bowel reminders as possible. Note the use of "chocolate kisses," yellow icing, the big crack, and even the word "bun" in the inscription. Now that's a true master at work.
If the shower is around Halloween, you'll also have this fun option:
Yep. A subtle insinuation that mom-to-be rides a broomstick (or has one shoved where the sun don't shine) oughtta do the trick.
Or, heck, while you're at it: why not take a stab at mom's drinking habits?
Now sit back, relax, and revel in the knowledge that no one will ever trust you to order a cake, ever again.
Thanks to Crystal B., Stephanie S., Jenny C., JK, & Angie M., who haven't ordered a cake since 1999.