Planet Zebes (惑星ゼーベス, Planet Zebesu) serves as the lone Metroid installment stage for Super Smash Bros. Like most other stages, it did not return in Super Smash Bros. Melee, and is banned in N64 Backroom tournaments for its acid that interferes with usual gameplay, though is sometimes allowed in non-official tournaments on behalf of its size ideal for aerial combos. It is also occasionally allowed as a counterpick over Peach's Castle due to the larger size.
Planet Zebes consists of a rough, jagged base, three main platforms (one of which is sloped at an angle), and one smaller platform ascending and descending to the far right of the stage. Hazardous acid surges below, periodically submerging most of the base and two of the three platforms, though never rising high enough to reach the topmost platform.
Touching the acid results in damage and serious knockback, capably KOing a player if their damage meter is high. It can also however be used strategically as a means of salvage if risen enough; in the event of a player being knocked off of the stage and into the acid, it will launch them skyward, allowing them to reuse their recovery or simply fall back onto the stage. Obtaining a Starman (or any form of invincibility) grants invulnerability to the acid, allowing the player to walk through it with no obstruction. However, if, while invincible, the player falls off the stage and through the acid, he or she will self-destruct. It will not "bump" the player up, as they are immune to its burn.
 Comparison to Brinstar
Some stages in Super Smash Bros., while not directly returning, were recycled or heavily modified for Melee, Planet Zebes and Brinstar being one such example.
There are several other minor details. A cluster of organic material conjoins the base of Brinstar and splits the stage in two when destroyed. Also, Ridley is no longer seen flying in the background, but is instead replaced with a giant throbbing alien organism, as well as a Chozo Statue that occasionally gets up and roams about.
This stage is purportedly inspired by the Brinstar area of Planet Zebes in Metroid, however the only clear reference is the yellow acid featured in some rooms harmful to the player upon falling in. Metroid II: Return of Samus would also have acid hinder the player from further excavating the planet's depths, to which killing enough Metroids ruptures an earthquake and sinks the acid, allowing safe progression. Contrarily, toward the end of Super Metroid, in Mother Brain's room an earthquake occurs and acid begins to rise. While originating in Metroid, the acid on the Planet Zebes stage rises and falls flippantly, potentially referencing both Metroid II and Super Metroid.
Corresponding to typical Metroid platforming, the stage does appear suspended amidst a large vertical shaft; its background textures also seem borrowed from that of Super Metroid. The music is based on the recurring main "Brinstar" theme originally heard in Metroid.
 Description from the Instruction Booklet
Anyone who touches the ebbing and flowing sea of acid on the planet's surface will be severely damaged.