I laughed too when my mom told me it. It originally goes, a baker was baking buns when one of the buns starts cheering in the oven. The bun goes, "I'm a bun! I'm a bun! I'm a bun! I'm a bun!" for quite awhile until finally the baker has had enough. He takes his shotgun and unloads a few rounds into the oven. Believing the bun to be dead, returns to doing his job until he hears, "I'm a donut! I'm a donut! I'm a donut! I'm a donut!"