Controls

Buttons

Y - Tongue
B - Jump
A - Aim egg/fire egg
X - Nothing
L/R - Freezes egg aim at current position

Movement

There is no run button, except when controlling super baby mario or the train vehicle. None of the other vehicles move faster when holding Y.
The quickest way to stop moving is to hold down, or to tongue a solid object.
Hold down while in the air to perform a ground pound.
Hold up while standing still to scroll the screen upwards, also makes baby Mario and Yoshi look up.

Combinations

File:Super Mario - Yoshi Island (J) (V1.0)001.png

Japanese thief minigames

Start + Select during a level that you have already beaten returns to the world map.
Pushing Y or down while aiming an egg cancels the egg throwing animation and swaps to the next egg.
Holding up while starting egg aiming starts the egg cursor pointing up and lets you aim lower than a "neutral shot".
To play free thief minigames directly from the map screen, hold Select and press the following buttons in order: X, X, Y, B, A.

Patient VS. Hasty

File:Hasty.png

Hasty Controls

Two options are accessible on the world map that change how the egg button works.
Patient is the default, and makes it so that tapping A once begins the egg-firing animation, and tapping it again fires the egg.
Hasty, on the other hand, sets it so that pushing A down begins the egg-firing animation, and releasing A fires the egg.
Most speedrunners use Hasty, which allows you to more easily fire off quick egg throws by just tapping the button once, as opposed to twice.