Tanoomba

Tanoombas are Tanooki-like Goombas found in both the Mushroom Kingdom and the Beanbean Kingdom. They resemble regular Goombas, except the Tanoomba has raccoon ears, a raccoon tail, and a leaf on its forehead. Tanoombas have powerful mimicry abilities and are able to transform into different objects and different creatures. However, Tanoombas can always be given away by the raccoon-like features or leaves that appear on their transformations.

''Mario & Luigi: Superstar Saga
During the events of Mario & Luigi: Superstar Saga, Tanoombas lived in an area north of Beanbean Castle Town. To attack, a Tanoomba will transform into a copy of Mario or Luigi (albeit a copy with a raccoon tail). After transforming, the Tanoomba will attack the brother who the shape-shifting Goomba didn't transforme into (i.e. if a Tanoomba transforms into a Luigi clone, the Tanoomba will attack the real Mario). This attack can be countered with a Hammer strike. Additionally, a Tanoomba can attack by spinning its tail at a Mario brother. The brothers can jump to dodge this attack, but should be prepared to dodge multiple tail strikes.

''Mario & Luigi: Partners in Time
Tanoombas lived on Thwomp Volcano during the events of Mario & Luigi: Partners in Time. On the mountain, Tanoombas use a variety of disguises to help them prey on unsuspecting travelers. A Tanoomba may turn into a friendly-looking Toad (with a raccoon tail), a 100 Gold Coin (with the Tanoomba's face on it), a ? Block (with a leaf on top), or even a Thwack (with the Tanoomba's face on it). Once a traveler approaches a disguised Tanoomba, the shape-shifting creature will reveal itself and attack.

In battle, the Tanoomba uses a variety of shape-shifting attacks (like their Beanbean counterparts, albeit different transformations). First, a Tanoomba may jump high in the air and either turn into a Thwomp (with a raccoon tail) or an orange balloon (with a raccoon tail). If the Tanoomba turns into a Thwomp, the shape-shifter will quickly fall to the ground and crush a Mario brother, causing massive damage. If the Tanoomba turns into a balloon, the creature will fall slowly to the ground, causing damage when it hits a Mario Bro. Both of these attacks can be countered with a Hammer swing, although the timing is different for each shape-shifting technique. Additionally, if a Tanoomba twirls in the air when it jumps, the monster will attack Luigi. If it jumps without twirling, the Tanoomba will attack Mario.

Besides turning into a Thwomp or an orange Balloon, a Tanoomba can also turn into a green Spiny shell (again, with a raccoon tail). When it transforms into the shell, the Tanoomba will slide into the Mario Bros., circling around and attempting to damage the brothers multiple times. This technique may even poison a Bro. if not avoided. To dodge this attack, Mario and Luigi have to jump as the Spiny shell approaches. Again, if the Tanoomba does a twirl jump before attacking, Luigi will be the first brother to be attacked. If the shape-shifter does a normal hop, Mario will be attacked first.

A stronger version of the Tanoomba that has been Shroobified, the Tashrooba, was created by the Shroob invaders during their conquest of the Mushroom Kingdom.

Trivia

 * The name "Tanoomba" is a portmanteau of the words "Goomba" and "tanooki." The tanooki is a raccoon-like creature from Japanese mythology. Like the Tanoomba, the tanooki is a master of disguise and a shape-shifter. Additionally, the tanooki needs to use magical leaves to help it use its powers.
 * The leaf on the Tanoomba's forehead is a reference to the Super Leaf of Super Mario Bros. 3, which transforms Mario into Raccoon Mario. Additionally, the Tanooki Suit is another power-up available in the same game.