Please note that I had renamed this article as the Spiny Shell. From my knowledge, the item is officially referred to by that name in Mario Kart series, and it also distinguishes this shell from the 'plain' blue shells also seen in Mario series (for example, the blue shell Mario can pick up and wear in New Super Mario Bros - it's also called the blue shell in this instance).
In my opinion, for that reason I think there should be two separate Blue and Spiny Shell pages. The Spiny Shell page I've been working on for Mario Kart series, and a Blue Shell page for plain blue shells seen in other Mario platforming series.
There is a problem though with creating these two articles - both the 'Blue Shell' and 'Spiny Shell' titles give a double redirect to one page and this prevents separate articles from being made. Would any of you be able to fix this problem?