Bombshell Koopas (originally known as Nokobons, also known as Boomba Troopa) are enemies from Super Mario Land and Super Luigi World: The Big Adventure. Like regular Koopa Troopas, they do not die when jumped on, but instead retreat into their Bomb Shell. The player can throw them, however, even if the player is holding them, they will eventually explode.
They also appear in New Super Mario Bros.: Twist It! in levels 16 and 18. In Level 16, they can only be killed by POW Blocks, and Mario has to land on the POWs to blow them up. Two appear in this level and if he hits them, he will be instantly killed. There are also POW Blockhoppers in this level. In Level 18, they appear in the Bowser fight, but only one. It just causes problems while Mario tries to avoid hitting Bowser as he knocks himself into the lava.