A Whirly Gate is a type of door that appears in Yoshi's New Island. When Yoshi enters a Whirly Gate, he transforms into one of the six power-ups in the game. The power-up he gets when he enters the door depends on the symbol above the door depicting a sketch of the power-up.
The Whirly Gate reappears in Yoshi's Woolly World. These often contain stamps, Smiley Flowers and/or Wonder Wool.