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 one of many future Yoshi's "Kirby-eque transformations" (as the author calls them, in volume 8) during 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 whith his face on it. While he's 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 hammer to Mario, but they don't 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 gets defeated. While Mario and Luigi grab the hammers to maybe use them later, Yoshi returns to normal, with the big hammer still stuck in his mouth, and screams in fury that he doesn't want to hear the word "hammer" ever again.

In chapter 4 of volume 4, Mario and Yoshi dives inside the SNES Lake. This teleports them in 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 getting healed, and, during the battle against Agahnim, he tires to defeat him by eating and spitting back his spells, with no success of hurting him. After defeating the sorcerer, Mario and Yoshi can leave by diving in Hyrule's SNES Lake, and Yoshi returns to normal once out from the Zelda world.