Kaboomba

The Kaboomba is a walking cannon enemy that first appears in Super Mario World 2: Yoshi's Island. Its name is supposedly a portmanteau of "kaboom" and "Goomba", despite Kaboombas having no relation to Goombas other than being walking enemies.

Super Mario World 2: Yoshi's Island
Kaboombas only appear in The Cave Of The Mystery Maze and Raphael The Raven's Castle. They attack by shooting heavy cannonballs that fall to the ground and explode after a few seconds. Yoshi can safely stand on them, and eating them does nothing. An egg or Ground Pound disposes of them.

Yoshi's Island: Super Mario Advance 3
Kaboombas retain their role in the Game Boy Advance port, Yoshi's Island: Super Mario Advance 3.

Yoshi's New Island
Kaboombas make a return appearance in Yoshi's New Island.

Super Princess Peach
Kaboombas also appear in Super Princess Peach, where they are named Cannons. The Calm Cannon, a sleeping variety, also appeared.

Other appearances
Kaboombas and an unused big variant were originally designed during the development of Super Mario World, where they would have shot Green Shells. They would have had white shoes, which also appear in early assets of Super Mario World 2: Yoshi's Island.

Super Mario World 2: Yoshi's Island

 * Shogakukan guide: 歩きながら弾をポロポロ落とす、しまりのないヤツ. 近よると危険. (A clumsy guy who drops projectiles while walking. Dangerous to approach.)
 * Player's Guide: He strolls slowly, but unleashes a painful payload. It's pretty easy to evade this cantering cannon.

Yoshi's Island: Super Mario Advance 3

 * Shogakukan guide: 発射された弾は飲みこめないので要注意. 上に乗ることもできるが、弾に当たりやすくキケンだ. タマゴで倒すか、逃げよう. (Be careful, as the fired projectiles cannot be swallowed. You can ride on top of it, but it is dangerous because it is easy to get hit by a projectile. Use an egg to defeat it or run away.)

Yoshi's New Island

 * Shogakukan guide: 正面の斜め上に弾を放ちながら、ゆっくり歩く. 弾は山なりに飛ぶが、飛距離は短い. 弾がじゃまになって動きにくいので、本体をヒップドロップで倒そう. (They walk slowly while shooting projectiles diagonally up in front of them. The projectiles fly in a steep angle, but the distance is short. Since the projectiles are a nuisance and make it difficult to move, Hip Drop the main body to defeat it.)

Super Princess Peach
63: An annoying enemy that attacks with cannonballs.
 * Glossary

Trivia

 * The Player's Guide description for the Kaboomba is erroneously accompanied by an image of a cannonball fired from a Kaboomba, instead of the enemy itself.