It's not just Mario that inexplicably suffers a cull on 31st March; you'd be excused for forgetting that another Nintendo title is due to drop off the Switch eShop at the end of this month.
Fire Emblem: Shadow Dragon & the Blade of Light is in its final hours on the store; it was pretty big news when it was announced and then finally released on 4th December last year. Previously a Famicom exclusive, it was the first time that the series debut had been released outside of Japan, with a handsome physical edition catching the eye.
Though the limited production run of the collector's edition is perhaps understandable, Nintendo's decision to limit its release window on the eShop was met with some bafflement, albeit it hasn't generated the same attention as the upcoming Mario purge.
Of course, as the first game in the series this title is relentlessly old-school, but if you want a digital copy on your Switch now is the time to pick it up.