Spiky Stardust Defense System
From the Super Mario Wiki
The Spiky Stardust Defense System, also abbreviated to SSDS, is an obstacle in Mario & Luigi: Superstar Saga. It is only found in Stardust Fields, serving as an early tutorial for using Mario and Luigi's jumps in tandem. It is a series of glowing spikes that extends from one of the ground to the other. If either Mario or Luigi lands on it, both of them are sent flying back to just before the obstacle.