Yellow Shell

The Yellow Shell is a Koopa Shell introduced in Super Mario World. It gives Yoshi the ability to create sand clouds that defeat nearby enemies upon landing. It also allows Beach Koopas to turn shells into Flashing Shells. It has recently been introduced as an item in Mario Kart Twinsanity, where it acts like a Red Shell, except it traps its target in the ground for a few seconds.

Koopa Kart: Double Trouble!! (2004)
The Yellow Shell is Cheep Cheep and Doopliss's Special Item in Koopa Kart: Double Trouble!!. It can be obtained from 4th to 9th place. When used, it will act like a Red Shell, except it will cause an earthquake that will trap its target into the ground.