From the Super Mario Wiki
Terekuribō (literally "Boo Goomba" or "Goomboo", from Teresa, the Japanese name of Boo, and Kuribō, the Japanese name of Goomba) are undead Goombas found in Super Mario Land 2: 6 Golden Coins. It is essentially a cross between an ordinary Goomba and a Boo. This results in an enemy that is invincible as a Boo but moves and acts as Goomba. Green Shells and Starmen are effective in defeating it. It is found only in the schoolhouse level of the Pumpkin Zone.