Bob-omb has two white eyes, a fuse, two legs, and usually has a wind-up mechanism on its back. The mechanism is not required to make the Bob-omb work, however.
In Super Smash Flash
It is one of the many throw-able items featured in Super Smash Flash. When thrown, it has huge knockback, and causes a lot of damage. Because of SSFs damage set and physics, a flaw may cause more than 1000% of damage to occur if a player throws a Bob-omb at a chain of, either, other Bob-ombs or activated Motion-Sensor Bombs with another player standing on them without offering any knockback.
In Super Smash Flash 2
Bob-omb is upgraded in Super Smash Flash 2 to work very similar to its Super Smash Bros. series' counterpart, where it appears as a dangerous item that can be picked up and thrown, they have a small yet powerful explosion on contact. Unlike SSF, if it is left alone for too long, however, it will light its own fuse and start walking around, blowing up when someone touches it, either directly or indirectly, or after a 15 seconds pass. Attacking or hitting the Bob-omb makes it explode instantly so players must be careful. It can do up to 27% of damage.
Bob-omb, under the name Bob (ボブ), originally first appeared in the non-Mario game, Yume Kōjō: Doki Doki Panic, as an enemy dropped by a flying bird enemy called Tondoru (トンドル, called Albatoss in the western), eventually exploding on its own. Even since its debut, the player could pick and throw Bob to their advantage, such as using its explosion to defeat other enemies or destroy some walls, the explosion itself is also harmful for the player. When the original Super Mario Bros. 2 (subtitled in the western as the The Lost Levels, sáns the 2) was deemed too difficult for the North American audiences, Nintendo picked Doki Doki Panic to localize a Super Mario Bros. 2 for North America and eventually Europe. Thus, this Super Mario Bros. 2 became the first game that formally turned Bob, now under their current name of Bob-omb, as a proper Mario character. Since then, Bob-ombs have become recurring enemies in the Super Mario platforming series, now serving under Bowser's Koopa Troop. They have also become common explosive items in the Mario spin-offs, most notably in the Mario Kart series.