From the Super Mario Wiki
“THOU ART TOAST!”
While in Sector Seven of The Overthere, Mario encounters a Nimbi fighting the invading Skellobits. Upon Mario's arrival, the Nimbi requests Mario's help in defeating the Skellobits. Once his request is granted, the Nimbi - whose name happens to be Rebbi - gives Mario the Red Orb, one of the three orbs required to build the bridge to Grambi's castle.
Later on, beyond the bridge, Mario and his party are stopped by a massive squadron of Skellobits and Skellobombers. Rebbi shows up to help the heroes defeat them. After recovering his health and strength, Rebbi manages to gather a brigade of Nimbis, who then engage the Skellobombers in a fierce aerial battle, thereby allowing Mario and Co. to head for Grambi's castle without any interruptions.
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