Yoshi's Island is a stage confirmed for SSBB. It has a horizontal design, with 2 main platforms. The top one tilts during play. There is a ghost, called the "Support Ghost" who sometimes saves players thrown off. The stage will also change between the 4 seasons during the match.
The official website has posted a clip of a theme song for a Yoshi stage, though it is unknown if it is for this one or a different, unconfirmed one. It is an upbeat remix of the Yoshi's Story ending theme.