Morph bubble

Morph Bubbles are floating bubbles found in Yoshi's Island in Super Mario World 2: Yoshi's Island and its sequel Yoshi's Island DS. When a Yoshi touches this, the Yoshi will turn into a different form. Some transformations are temporary, while others last until the transformed Yoshi hits a Yoshi Block. If a Yoshi is transformed into a temporary form, it must hit a Yoshi Block to turn back to a normal Yoshi, or pop another Morph Bubble to stay in that transformation a little while longer.

Transformations
The transformations marked with an asterisk are not in Yoshi's Island DS.
 * Yoshi Helicopter
 * Yoshi Mole Tank
 * Yoshi Submarine
 * Yoshi Car*
 * Yoshi Train*
 * Ski Yoshi (Skis)
 * Snowball Yoshi
 * Yoshi Plane (unused)
 * Yoshi Tree (unused)
 * Yoshi Mushroom (unused)