Yoshi Demo is a tech demo that appeared to be a Game Boy Advance port of Yoshi's Story. It is also commonly regarded as vaporware, though it is unknown Nintendo ever had any intentions of releasing it as a full game. The first version of the demo is completely mute, but the second version contains music and sound. The demo's ROM image can only be obtained within the Game Boy Advance SDK.
As stated above, this tech demo seemed to be based on Yoshi's Story, though it had a few differences from that game. Yoshi Demo begins by showing Yoshi's Island rotating before cutting to an endless, Yoshi's Story-like level. At the beginning of this level, Yoshi was given three Yoshi Eggs; though IGN claimed that Yoshi could lay more eggs by eating enemies, this was never proven true and Yoshi's eggs would actually appear to have acted as health in Yoshi Demo, as he lost both a Yoshi Egg and a petal from his health meter when getting hit by an enemy attack and regained three petals upon collecting another egg. Health could also be collected by hitting Message Blocks and Ground Pounding the balloon that resulted. Also, when Yoshi ground pounded, he would pound the ground with his head. Yoshi Demo would have introduced Toadies that would attack Yoshi with spiked balls and Thwomp-like weight enemies.