It produces a growing explosion that traps players in its radius. Players trapped in the explosion get repeatedly at 1%. Players can usually not escape the explosion but can move with Directional Influence. The knockback from the explosion can kill but does not for typical damage levels. The Yellow Devil on Wily's Castle causes a similar effect after being defeated.
There is a small chance that a Smart Bomb will turn out to not explode; instead of going off it makes a distinctive echoing noise and travels through its target, causing flinching but no knockback. However, the smart bomb is still dangerous and can explode from attack and even at random.