Here's an interesting tidbit that we get several emails about every month.
Starter (the doomed heir to Portal) was released in July of 1999, and the Mercadian Masques expert-level expansion was released in October of that same year. Both contained the card Squall, but each had a different mana cost. The Starter version cost , and the Masques one was .
How did that happen? Unclear. There's a note in the Masques file from the head of R&D telling the developers to synch the Masques Squall up with the Starter version, but apparently someone changed one of them at the last minute.
As with other mana cost discrepancies (such as the Alpha/Beta Orcish Artillery and Oriflamme), the Oracle is the final arbiter, and that document sides with the Masques cost, meaning that Starter Squalls are tournament legal, but they must be played as if they cost . The later appearance of the card in Seventh Edition further cements the cost as correct.