Morph ball

The Morph Ball
The Morph ball is a power possessed by Samus Aran which allows her to move through tight spaces. It first appeared in Super Metroid for the SNES.

In this state, she can move through tunnels and pipes which often leads to puzzles (and the game Metroid Prime Pinball for the DS). Samus can also drop bombs in this state which can be used to damage enemies or to perform a jump.

In Smash Bros.
In the Smash Bros. series, the morph ball has appeared as Samus' down B attack. She briefly turns into the morph ball and drops a single bomb. This could, however, be done in rapid succession.