Some Mario Kart games put small hearts on the asphalt in parts of tracks that are extremely difficult to notice due to their size, the player’s speed, and their oblique angle to the camera.
Top: in Mario Kart: Double Dash, there are hearts on the ground in the pink alley shortcut through the downtown area in Mushroom City.
Bottom: in Mario Kart 8/Deluxe, there are extremely faint hearts on the ground on the main road of N64 Royal Raceway. Note that while these are also shaped like clover leaves, they are overwhelmingly likely to be hearts since pink hearts are found elsewhere on the course while clover iconography is absent.
