The heart-shaped acorn is a gift that Sandy gives to SpongeBob. It appears in the episode "Valentine's Day," the books The World's Greatest Valentine and Deep-Sea Tales, and the video game SpongeBob's Truth or Square.
It is a large acorn in the shape of a heart. It has a wooden arrow through its center.
When SpongeBob walks to Sandy's treedome on Valentine's Day, Sandy gives the acorn to him and says "Happy Valentine's Day, SpongeBob! I'm nuts for you." SpongeBob puts it in his pocket before giving Sandy a chocolate syrup heart.
The World's Greatest Valentine
The heart-shaped acorn has the same role as in the episode.
It appears in a reprint of The World's Greatest Valentine.
SpongeBob's Truth or Square
It is a happiness object in the second level, "Meeting Sandy Cheeks." If the player completes a tiki challenge and picks the acorn up, it is added to their object collection. In the Xbox 360 version, finding the heart-shaped acorn will give the player the "Valentine's Day" achievement.