Blocks are environmental units appearing in the Super Smash Bros. games, originating from the Mario, Ice Climber and Kirby series. They can normally be broken by any attack, and come in different colors and sizes (all are cube-shaped). While breakable variants do not appear, there are POW Blocks in the Mushroom Kingdom stage in Super Smash Bros.
Breakable blocks (bricks) appear in Melee in the first level of the Adventure Mode and on the Mushroom Kingdom. They are accompanied by ? Blocks, which release items, and occasionally, if all blocks disappear, there is a chance that they all reappear as "?" Blocks. Blocks notably slow down knockback of characters flying into them. They can be teched on as well. There are also item blocks ("!" Blocks) in Princess Peach's Castle, but are more akin to their video game of origin's counterparts in that, once hit, become unmarked and no longer release items. These particular blocks come in three colors: red, blue, and green, and appear when a switch is pressed somewhere on the castle. This is a reference to the switches in Super Mario 64 and even Super Mario World which are used to solidify blocks which were previously outlines of blocks appearing in certain levels/courses. On Yoshi's Island, yellow blocks with eyes appear. They can not be broken, but when hit, will become two-dimensional and flip (allowing players to go through them). They eventually return to their solid state, where they can be hit again.
On the Green Greens stage, star blocks appear on either side of the stage in between the main and outer two platforms. They fall from the sky and land on candy cane-colored railing, which appears to connect each platform. Like the bricks in the Mushroom Kingdom stage, they can be broken with regular attacks and teched on (but break in the process), but one difference is that rather than slowing down knockback, characters thrown into the blocks (especially from afar) will be bounced back. Occasionally, explosive star blocks that flash and have bomb symbols on them rather than stars will fall. If one attempts to break a bomb block, they will take damage and be sent flying. The invincibility frames characters get from teching protect them from the explosions should they ever be knocked into one from below.
Ice blocks appear on Infinite Glacier: Icicle Mountain. Like their Kirby and Mario counterparts, they can be broken with regular attacks. They come in two sizes: small and large. Unlike the other blocks, they are much harder, and characters bounce off of them when thrown into them. Ice blocks have their own properties as well, similar to the ice platforms, in that characters have less traction when walking on them. On the Ice Climbers' Target Test are "blocks" than can be broken with regular attacks, but are needed to climb to the top and reach the rest of the targets.
? blocks appear on the Mushroomy Kingdom stage in Super Smash Bros. Brawl, serving the same purpose as they did in Melee, yet with a more rustic and aged appearance, as the stage invokes. These blocks will not respawn as in Melee. Mario also breaks one of these ? blocks to reveal a Mushroom in the Opening Movie. The blocks on the past stage Yoshi's Island also appear, with the same properties as before.
Blocks return on the past stage Green Greens with the same properties as before.
Breakable blocks appear throughout the Subspace Emissary in different shapes and colors. Most are regular blocks capable of being destroyed by attacks, but others are only destroyed via chain reaction from a single bomb block.