Yoshi can leave a Berry motionless in mid-air if you turn around while grabbing one with your tongue to eat another one. Ideal course: Yoshi's House.

Similarly, while carrying a Baby Yoshi, try to eat another enemy while the Baby Yoshi is going through the growing transformation--that enemy will drop to the "background" and cannot be stomped or touched, nor can it touch you. Ideal course: Star World 4.