They are black, spheroid wind-up bombs that explode to attack the player. They are recurring enemies in many Mario games. They often cameo in SMG4's bloopers as they are common enemies in Super Mario 64.
They also have good variants called Bob-omb Buddies which are pink and have no fuses that are allies of Mario. There is also a Bob-omb named Bobby who appeared in SM64 Bloopers: Smexy Soccer.
