Cog (obstacle)

Cogs (also known as Gears) are obstacles in some Mario platformers. They have the ability to push the player off if one tries to climb one.

Yoshi's Story
Cogs appeared in Yoshi's Story in the Mecha Castle. They push you back and it's shown here at 5:57 that they can make a Yoshi lose a life. They are wooden and can only make a Yoshi lose a life if the player rushes to two of them and they are spinning towards each other.

New Super Mario Bros. Wii
In New Super Mario Bros. Wii,  includes them. If the player remain under one, they will be squished and will soon lose a life.

New Super Mario Bros. U
New Super Mario Bros. U brings back cogs in Crushing-Cogs Tower. They serve as platforms so the player can reach the top of the tower to fight Boom Boom.