Bob-ombs are a species found throughout the Mario series. They are small bomb-shaped beings who can create explosions by detonating themselves.
Super Mario Bros. 2
In Super Mario Bros. 2. Black Bob-ombs are generic enemies that make frequent appearances. They light their fuse upon being provoked, often achieved by jumping on them. Depending on the game, they walk in a straight line or follow the player in an attempt to cause damage when they explode, which occurs shortly afterwards.
Super Mario 64
Red Bob-ombs are friendly, and are found in Super Mario 64 among other games. They are known to give advice, open cannons for use, and operate various devices in an attempt to help Mario. In the first level, Bob-omb battlefield, the Red Bob-ombs were locked in a war against the generic black Bob-ombs and their King, whom Mario had to destroy to get the game's first power star.
Mario Party series
In the Mario Party series, they appear in many mini-games. In Mario Party, the both the red and black Bob-ombs appear on the board Wario's Battle Canyon where both sides are at war. However, it is resolved by the Superstar at then end. Bob-bombs also appears as partners in Mario Party 3 where one serves as Wario's main partner. One also appears in Mario Party 4 to announce that a Battle Minigame is about to happen, replacing Goomba from the previous game. In Mario Party 5, they appear in orbs to throw to another space. If you step on that space, you'll lose coins. They also appear in the 4 player Minigame Dodge Bomb as an item to throw and in another 4 player minigame called Rumble Fumble, where they are an obstacle to the players. A weapon in super dual mode is called Bob-omb Cannon, which shot Bob-bombs. Another weapon in super dual mode is Bob-bomb wall, which is a very secret weapon. Bob-omb has been in most of the other Mario games alongside Goomba and Koopa. Typically, they are in minigames as something to avoid or throw at other people. Although the Bob-ombs are known to be hostile, nobody seems to know why or how. They are commonly seen as servants to Bowser and even the other various villains in the series.
Super Mario Sunshine
Bob-ombs Reappear in a new electronic form. They only appear when Monty Moles throw them and in King Boo's lair when he spits them out. If Mario sprays water at them, they turn blue, allowing Mario to pick them up and throw them.
Mario Kart series
The Bob-omb is one of the items obtainable from Item Boxes. It can be thrown ahead of you, only to explode when someone drives past it. If no one drives by within a few seconds, it will explode on its own. Anyone caught in the blast will be spun out briefly. Bob-ombs first appeared in Mario Kart: Double Dash!!, as Wario and Waluigi's Special Item.
This item is normally obtained if you are in 2nd-6th place. Bob-ombs also star in their own Battle game in Mario Kart: Double Dash!!, Bob-omb Blast. In this game, drivers go through item boxes that only have Bob-ombs. Each kart can carry up to 10 (5 for each character on the kart). The Bob-ombs function the same way they do in races, and the players throw Bob-ombs at each other to gain points.
After Double Dash!!, Bob-ombs have appeared as normal items ever since.
contact with a player (or players), it will deal 30% damage with high knockback. When sitting for about 5 seconds, the Bob-omb will walk around on it's own for about 10 more seconds before exploding by itself. When near a ledge, a Bob-omb may even fall off and explode once hitting the ground.
In Paper Mario, friendly Bob-ombs can be seen living in Koopa Village. After a few of them escaped from Koopa Bros. Fortress, they lived up in the small town. Two Bob-ombs can be seen blowing up in Kooper's house and can be stopped by doing one of Koopa Koot's favors. The enemies appear in the Koopa Bros. Fortress where they serve under the Koopa Bros.. In battle, the Bob-ombs mainly attack by jumping into Mario. However, if the Bob-ombs are attacked, they will turn red attempting to explode on the next turn. Mario must be careful not to attack them directly or he'll take high damage. This can be easily dealt with using Kooper's Power Shell technique.
In Paper Mario: Sticker Star, Bob-ombs are first seen in Goomba Fortress where they rain down from the sky. Mario must actually use the Bob-omb to destory certain gates to proceed. Bob-ombs are also seen at Bowser Jr.'s Flotilla as regular enemies. In battle, they act much the same as in the previous games. Bob-ombs are also used as attacks by Bowser Jr..
Bob-ombs are more associated with Wario as they mainly appear on Wario's board Wario's Battle Canyon from Mario Party and one even appears as Wario's partner in Mario Party 3. Wario's special move from Mario Kart: Double Dash involves tossing Bob-ombs and Wario must fight King Bob-omb using Bob-ombs in Mario Kart DS. Mario Hoops 3-on-3 has a court named Wario Factory where Bob-Ombs come occasionally from elevators or conveyor belts. Those can be picked up and thrown to make them explode.
Oddly, during the end parade of Paper Mario, the Bob-ombs are shown to have arms. This is the only time that the smaller Bob-omb's arms are shown.