Shroob

The Shroobs are a race of Poison Mushroom-like aliens that attacked the Mushroom Kingdom when Mario and Luigi were babies. These events take place in the game Mario & Luigi: Partners in Time. They are a purple, mushroom-like species ruled by Princess Shroob and her older sister. They are from the Shroob Planet and most Shroobs carry ray guns with them. Unlike Toads, who are seemingly more human than mushroom, Shroobs seem to have retained most of their fungus ancestry.

They possess a massive fleet of flying saucers, which are powered by the vim of Toads. The saucers are capable of shooting energy bolts that turn people into Shroob Mushrooms, as well as causing devastating damage to houses and buildings. The Shroob military is very complex in their processes. They come in different colors and have different attacks. Unlike the Koopa Troop, the Shroobs have everything laid out in advance so that they could both protect vital operations and invade enemy regions at the same time.

Mario & Luigi: Partners in Time
They first started their invasion by destroying Toad Town and capturing many Toads. These Toads were taken to Toadwood Forest, where their vim was drained by the forest's genetically-altered trees. The vim was then collected at the Vim Factory, where Dr. Shroobs gave the vim to Swiggler, a terrifying, bio-engineered Wiggler. While guarding a Cobalt Star shard, Swiggler also drinks the vim and powers the Shroob UFOs.

Soon after, they started the creation of the mechanical Yoob and attacked Yoshi's Island. Yoob would eat any Yoshi it could find. These Yoshis would then be converted into more monstrous Yoobs and be used to attack the Mushroom Kingdom. During the invasion, Princess Shroob disguised herself as Peach to see the Mushroom Kingdom of the future and make sure her plan would succeed.

Mario & Luigi RPG 3
Three Shroobs appear in Mario & Luigi RPG 3 as optional bosses, this time these baddies were renamed as Shroob Seijin. They were inside blocks of ice in Bowser's castle, and when the player pushes a button, Mario and Luigi melt the ice, allowing the Shroobs to attack and be defeated once again. Additionally, Junior Shrooboids, broken Shroids and Commander Shroobs can be seen frozen in the battle's background, with also a big unknown form that looks a bit like Elder Princess Shroob, but it's probably not her, due to the fact she died. Although, she may have been revived by unknown means some point before the Shroobs were frozen.

Mario Hoops 3 on 3
A reference to Shroobs was made in the Mario Hoops 3 on 3 website where one of the player's baller names (determined by a five-question quiz) could be "Shroob Showstopper".

Super Smash Bros. Brawl
In Super Smash Bros. Brawl one appears as a sticker that raises launch power by seven.

Language
The Shroob language as it appears in the text bubbles in the game is just a bunch of nonsensical small picture text. When the Shroobs talk in the game, they make gibberish sounds. However, they do sometimes use the Latin alphabet, as seen in the battle against Shrooboid Brat. When the Shrooboid Brat was about to attack, the Shroob crowd raised up signs that said either "M" or "L", signifying who to attack. The Elder Shroob Princess can also speak English. Later on, the language is shown to players using subtitles in parentheses. Whether or not this means that Mario and Luigi begin to understand the language or is just for purposes of clarification is unknown.

Shroob Leadership

 * Elder Princess Shroob
 * Princess Shroob
 * Commander Shroob

Shroob Monsters

 * Swiggler
 * Yoob
 * Sunnycide

Shrooboids

 * Junior Shrooboid
 * Shrooboid Brat
 * Elder Shrooboid

Shroobs

 * Shroob UFO
 * Shrooblet
 * Dr. Shroob
 * RC Shroober
 * Shrooba Diver
 * Guardian Shroob
 * Blazing Shroob
 * Shroid
 * Support Shroob
 * Shroobsworth
 * Intern Shroob
 * Shroob Seijin

Shroob Creatures

 * Spiny Shroopa
 * Lakitufo
 * Shroob-omb
 * Tashrooba
 * Shroob Rex
 * Shroob Chomp