Eighth Edition uncommon. Though it’s quite obscure, “Megrim” is actually a real word. Derived from Middle English, it’s an alternate word for “Migraine”. In Magic flavor, cards in hand are like spells in a wizard’s mind, so discard spells are often flavored as magic that traumatizes the mind.
Ninth Edition, the Alpha version of this card was misprinted with the incorrect casting cost of just 
Ninth Edition rare. One of the most non-intuitive parts of the core set has always been that the creature lords didn’t share the creature type of their minions. With Ninth Edition, all the lords have been changed to match their minions, but only the lords that made it into the set — sorry, Lord of Atlantis!
Ninth Edition hits stores, of the five circles of protection, only COP: Red will have appeared in every core set! (The circles against white, blue and green will not be in Ninth Edition, and COP: Black was inadvertently left out of Alpha.)
Saviors of Kamigawa common. While the merits of this card in draft were the subject of considerable debate at Pro Tour London this weekend, the original version would never have had doubters. During design, this creature had the same stats and casting cost, but only took one life coming and going! (Yeah, that turned out to be too good.)
Visions uncommon. This future tournament star was first printed in Visions. However, players were able to see it four months early thanks to the Multiverse gift set, released in November 1996. The set included non-English boosters as well as two ???preview packs??? of Visions. (25 different Visions cards could appear in these special packs.)
Urza???s Destiny common. Occasionally promotional versions of cards are released with alternate art. If you purchased Duelist #39, you got a version with special art by Carl Critchlow. (Click here to see the promo Scent of Cinder, and note that collector number, 96a/143!)
Fallen Empires uncommon. The Alpha version of Cyclopean Tomb is the most famous card for being printed without a mana cost, but it’s not the only one. When Breeding Pit appeared in Italian Fifth Edition as Abisso Prolifico (click to see), it also had no casting cost.
