Power-up in the Mario Kart series
The Spiny Shell, colloquially known as the blue shell, is a power-up item in the Mario Kart video game series. Originating in Mario Kart 64 (1996) and featured in every main entry of the series since then, the Spiny Shell, when used, aims directly at the racer in first place, stopping them on impact. The Spiny Shell acts as a "catch-up"...
Y when you're on the giving end, N when you're on the receiving end.