From the Super Mario Wiki
The Lovely Seashell is a key item in Mario Party Advance. Goombob asks the player to obtain it for him, as he wants to give it as a gift to his crush, Goombetty. It can be found at the Sandy Beach. Once the player returns to Goombob Manor, Goombob excitedly asks for the seashell, at which point Goombetty walks in. She notices the seashell, which prompts Goombob to give it to her and ask her out on a date. She says that the seashell is pretty and agrees to the date. Goombob jumps in joy and gives the player the Dessert Menu Gaddget as a reward.
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