Mecha-Bomb-Koopa is a enemy appears in various games in the Mario series.
Mecha-Bomb-Koopa is identical to a normal Mecha-Koopa, but its look is slighty different, as instead of a key on the back of it there is a fuse like Bob-ombs. Its color varies in different games, as it's black in Newer Super Mario Bros. U and it's red in Super Mario World U.
Mario 3D World
Mecha-Bomb-Koopas were originally supposed to appear in the game, but they were scrapped from the final game for unknow reasons.
Newer Super Mario World U
Mecha-Bomb-Koopas first appear in Newer Super Mario World U. They only appear in Iggy Koopa's airship, and in this game they'are black. They behave exactly like ordinary Mecha-Koopas, but if the player(s) jump on them, they will explode in a few seconds like a Bob-Omb.
Super Mario World U
The Mecha-Bomb-Koopa reappear in Super Mario World U. They are identical to the previous games they appeared in but this time they are red. When they are jumped on the are unable to move but the fuse will light up. Instead of kicking them around like Mecha-Koopas the player can pick them up and toss them like Bob-ombs.
They look like them in Super Mario World U, and act the same, there only on World 2 airship, there is a sub-species, called Bombshell MechaKoopa that detonates only if stomped on 3 times.