Mega Guy

Mega Guys, also known as Big Shy Guys , Giant Shy Guys , or Mega Shy Guys , are Shy Guys that are larger than normal.

Super Mario World 2: Yoshi's Island/Yoshi's Island: Super Mario Advance 3
In Super Mario World 2: Yoshi's Island and its GBA remake, big Shy Guys appear during the boss fight with Froggy. Yoshi must eat them to produce the Giant Eggs needed to damage the boss. These big Shy Guys are technically about the size of a regular Shy-Guy, if not actually smaller, but are large in relation to Yoshi and Baby Mario, who are shrunken by Kamek.

Yoshi's New Island
In Yoshi's New Island, Mega Guys spawn from large pipes, and unlike the game's regular-sized Shy Guys, they are impervious to stomps and constantly walk forward, only turning around once they reach a wall. Yoshi can swallow them to turn them into Mega Eggdozers, which can be used to destroy otherwise indestructible obstacles. Mega Guys require a bit more effort than normal to swallow, as the player has to rapidly press to do it. A metallic variant known as Metal Guys also appear, which are used to make Metal Eggdozers.

Super Mario Advance
Big Shy Guys appear as semi-common enemies in Super Mario Advance. They act much like ordinary Shyguys, aside from being twice as large, and come in red-robed and blue-robed variants just like ordinary Shyguys, with the difference being that blue-robed Big Shy Guys turn around at ledges, unlike red-robed ones that walk off of ledges instead. They release Hearts when thrown to the ground or defeated, and take longer to pick up compared to most enemies and items due to their large size. Their unique traits are largely similar to those of Big Ninjis, which also appear in Super Mario Advance.

Super Mario-kun
In the small short that concludes the chapter in volume 26 of Super Mario-kun, a Big Shy Guy attacks Mario, Goombario, and Kooper. It then pits Mario against Robirdo. Mario, however, grabs the Big Shy Guy and throws it against Robirdo, defeating both.

WarioWare: D.I.Y. Showcase
In WarioWare: D.I.Y. Showcase, a Big Shy Guy is one of the enemies that can appear in the microgame Mario Adv.

Mario Tennis Aces
In Mario Tennis Aces, a black Mega Guy appears in Snowball Fight, acting as a regular Shy Guy. In addition to the aforementioned type appearing in blue, in Ver. 2.3.0 onwards, much bigger black Mega Guy bandits wearing yellow or red bandanas are encountered individually in the added Shy Guy Train Tussle Co-op Challenge. They have increased health and can be attacked by either hitting back the projectiles shot by the four cannons overhead or hitting back the Bob-ombs or Mega Bob-ombs tossed by it. When defeated, they drop a key to a golden treasure chest with coins.

Other appearances
Big Shy Guys appear in an early trailer of Yoshi's Story, though they are not present in the final game. They also appear in the Yoshi Demo, where stomping one would turn it into a regular Shy Guy.

Yoshi's New Island

 * Shogakukan guide: 通常サイズより何倍も大きいへイホー. 舌を伸ばしてボタンを連打すると、メガタマゴを作ることができる. メガどかんから出現することが多い. (A Shy Guy that is many times larger than normal. By extending your tongue and pressing the button repeatedly, you can create a Mega Eggdozer. They often appear from Mega Warp Pipes.)