From the Super Mario Wiki
The Cobalt Necktie is a special item, an equippable accessory that is obtained from the Starbeans Cafe in Mario & Luigi: Superstar Saga and its remake. It is the sixth special item Mario and Luigi receive from Professor E. Gadd after brewing a unique blend that has not been brewed before. When a brother has the Cobalt Necktie equipped, his STACHE stat points are doubled.
In earlier versions of the game, the Cobalt Necktie had a drastically different appearance and name. Called the UV Lamp, the item was originally supposed to be handed out by a small cameo appearance of Captain Olimar rather than Professor E. Gadd. While the name has changed to reflect a different item, no unique sprite for the UV Lamp has been found.
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