Shield Yoshi

Shield Yoshi is an original Yoshi form that only appears in two chapters of the Super Mario World story arc in Super Mario-kun. It's the first of many future Yoshi's "Kirby-eque transformations" (as the author calls them, in volume 8) in the manga.

In chapter 10 of volume 1, while fighting an Amazing Flyin' Hammer Brother, Mario finds a Dragon Coin. Yoshi, mistaking it for a chocolate coin, eats it and is transformed into a shield with his face on it. While he is scared and pleading to be back to his normal form, Luigi suggests to Mario to use Yoshi's new form to protect himself against the Hammer Bro's hammers. Mario follows his suggestion and flies towards the enemy, who is tossing all of his hammers at Mario, but they do not stop him, since Yoshi is the only one to get hurt. Lastly, the Hammer Bro tries to stop Mario with his last hammer, a gigantic one, but it gets stuck in Yoshi's mouth and the enemy is defeated. While Mario and Luigi grab the hammers to potentially use them later, Yoshi returns to normal, with the big hammer still stuck in his mouth, and screams in fury that he does not want to hear the word "hammer" ever again.

In chapter 4 of volume 4, Mario and Yoshi dive inside the SNES Warp Zone. This teleports them to A Link to the Past, where Mario is armed with the Kinoko Sword and Yoshi is stuck in his shield form. During the whole adventure in Hyrule, Shield Yoshi accompanies Mario either by hopping behind him or by getting carried by him. He eats a Fairy, robbing Mario of the chance of being healed, and, during the battle against Agahnim, he tries to defeat him by eating and spitting back his spells, with no success of hurting him. After defeating Agahnim, Mario and Yoshi leave by diving into Hyrule's SNES Warp Zone, and Yoshi returns to normal after leaving the Zelda world.