If you are pregnant this Halloween, get a big box, like one that a TV or microwave comes in, cut holes for your head, and arms leaving the bottom open so you can have lots of room for your legs. Make sure to get one that will go below your belly.
Decorate it as an oven by painting it, make sure to put controls. You could even buy some old controls at a thrifty shop and glue them on. Cut a window in the front and paint lines around it like an oven door. Cover the place for the window with clear wrap so it looks like a window.
Then wear something tan (tan sweatshirt) over your baby. Your belly will show through the window and by wearing tan, it will look like a bun in the oven.