In the very first Magic release, several errors were made. One of which that affected game play was the printing of the wrong card type on Red Elemental Blast.
Meant to be an interrupt (as indicated by the card type of its blue counterpart), the card was printed as an instant. Under the old game rules, that meant it could not actually be cast at the right time to counter a blue spell, as only interrupts could be used in such a way.
The type was changed to interrupt for each subsequent printing of the card, from Beta to Fourth Edition. Of course, the introduction of Sixth Edition rules forced it to be changed again, via errata…
…back to an instant.