Cractus

From the Super Mario Wiki

Cractus is the second boss in the Game Boy Advance video game Wario Land 4. Cractus is also the guardian of the Emerald Passage. This strange monster resembles a giant, drooling cactus. If Wario touches Cractus' drool, the portly anti-hero will turn into a zombie, wasting precious time. He cannot attack Cractus while in this form. A firefly will fly by if this happens; by touching the firefly, its light will return Wario to his normal state. To defeat Cractus, Wario had to use the vines along the wall and slam into the monster's head from above.

In addition to the drool, Cractus can also attack by jabbing Wario with its cactus-like arms. Also, mere contact with the boss's toothed, gaping mouth will cause damage.

Cractus also appears in one of the ending scenes, chasing Wario.

Wario Land 4 Bosses
Spoiled Rotten | Cractus | Cuckoo Condor | Aerodent | Catbat | Golden Diva

Wario Series Characters
9-Volt | 18-Volt | Ashley and Red | Dr. Crygor | Dr. Payne | Dribble and Spitz | Goodstyle | Jimmy P. | Jimmy T. | Kat and Ana | Ken the Reporter | Mike | Mona | Orbulon | Penny Crygor | Princess Shokora | Queen Merelda | Sewer Guru | Thang Family | Wanda | Wario | Young Cricket and Master Mantis
Major Villains
Captain Syrup and the Black Sugar Pirates| Denpuu | Awazon Genie | Rudy the Clown | Golden Diva | Black Jewel | Count Cannoli | Terrormisu | Shake King
Minor Villains
Aerodent | Ball Bunny | Brawl Doll | Captain Skull | Carpaccio | Catbat | Clown-a-Round | Cractus | Cuckoo Condor | Dinomighty | Dual Dragon | Greenfist | Ironsider | Mad Scienstein | Mean Emcee | Red-Brief J | SandWorm | Spideraticus | Spoiled Rotten | Winter Windster