Mouse Ka-Boom is an orange mouse who is seen in W.A.R. Journal - Operation: Tiger Bomb. He is French, as he usually says "le" before a sentence or an action, as well as sporting a French mustache. He has protective goggles and a backpack full of bombs. His ears are bandaged and he is deaf from the explosions that he has been around. He fought alongside Flippy in the W.A.R. Mouse Ka-Boom is a explosives expert, as he can make bombs disguised as everyday things (such as apples).
One of his bombs would have killed the Tiger General, but it bounced off a pizza the general was holding. Mouse Ka-Boom accidentally caught it with both hands, but he couldn't get rid of the bomb because the cheese was making it stick to his hands. He ran to Flippy for help. Flippy used his knife to cut the fuse, but accidentally cut Mouse Ka-Boom horizontally in half. The lit fuse landed in his open back-pack full of bombs, causing a huge explosion. All that remained of Mouse Ka-Boom were several body parts and a lot of blood. According to Kenn Navarro, Ka-Boom's death is not permanent as his deafness will be explored in future episodes.
- Dynamite, frag grenades, nuclear bombs, old fashioned 19th century cannon bombs, and (according to popular rumor) a Molotov cocktail.
- His name sounds similar to Walt Disney's "Mouseketeers" from The Mickey Mouse Club (though this may just be a coincidence).
- According to Kenn Navarro, "Mouse Ka-Boom was originally supposed to be a big, burly rhino, the stereo-typical demolition man. The more we talked about him the more we felt like that was too on-the-nose. We finally decided to go against type and make him a little mouse with a giant back-pack FULL of explosives!"
- According to Kenn Navarro, Mouse Ka-Boom is deaf, making him the fourth character with a disability. The other three are Handy (amputated hands), The Mole (blind, with other senses limited), and Russell (amputated legs and missing an eye).
- Mouse Ka-boom may have been inspired by Mouser, an enemy boss in Super Mario Bros. 2 that threw bombs at the player.
- Since the series (so far) has been somewhat alike to WW2, Mouse Ka-Boom may be a reference to the French, an ally in WW2 that was taken over by Nazi Germany. There was a french resistance fighting the Nazis, so Mouse Ka-Boom may represent those French.