Secret Chippie Decoder Ring
From the Super Mario Wiki
A Secret Chippie Decoder Ring is a special ring worn by prestigious members of the Chimpmunks group. Shaped like a chipmunk's head, its use is unknown, and merely appears to be made out plastic. Mr. Gibbel is never seen without his Secret Chippie Decoder Ring, and while Mario won one of his own, he has never been seen with it.
The only appearance of the Secret Chippie Decoder Ring was in The Super Mario Bros. Super Show! live-action segment "Chippie Chipmunks", where Mr. Gibbel promised to award one to Mario if he became Chipmunk of the Month. However, it served as little more than a MacGuffin, and simply motivated Mario into performing acts of kindness towards Luigi so that he could win it.