King Bob-omb (or previously Big Bob-omb) is a giant Bob-omb who rules all Bob-ombs, as well as appearing as the first boss in Super Mario 64. He lives on the top of a giant mountain in the middle of the Bob-omb Battlefield.
His first real appearence in SMG4's bloopers was in the episode Mission For Peach where he attacked Mario for stealing his coins. He appeared again in Mini Italians where he guarded a mushroom and attempted to stop the shrunken italians.
His biggest appearence was in the sob story: A Tale of a Bob-omb where he fell in love with a Bob-omb that escaped the factory. At the end he was killed by Mario. He appeared much later in Super Mario Attorney where SMG4 helps him fly, but ended up plummeting and exploding onto the ground.
After a long absence, Big Bob-omb returns on a normal blooper, SM64 Bloopers: Casino, Cards and Chaos where he is named King Bob-omb and is one of the two main antagonists along with a Whomp. In this blooper, he appears in the casino and since Luigi was winning so many times, Big Bob-omb drugs him and Mario comes up with a plan where he must replace the casino's dealer. After succeeding, Mario says that Luigi wins 15 billion coins for not doing anything. This makes the Whomp and Big Bob-omb mad, so Mario and Luigi try to hide. After the Whomp got stomped by Dr. Eggman and Big Bob-omb got fooled by Mario, Big Bob-omb is defeated with the many coins from the slots. It is unknown what happened to Big Bob-omb after the Mario bros. leave the casino, as there was an explosion. He later appeared in SM64 Valentines 2017: GET THE GIRL!.