This seemed thematically appropriate for today.
In adapting the popular Super Mario franchise to the Game Boy, Nintendo’s developers made numerous changes along the way which have helped the titles to stand out — especially over the last decade or so, as the New Super Mario Bros. series has effectively embraced Super Mario Bros. 3 (and to a lesser degree Super Mario World) to the point of homogenization.
One change which stands out is the decision to use 1-Up Hearts instead of 1-Up Mushrooms as the item which represents an easy extra life. But when the 1-Up Mushroom is so iconic to the series, to the point that Nintendo has even merchandised it and its iconic sound (and only recently dropping the concept of extra lives in general with Super Mario Odyssey, but we’ll see how long that lasts), it’s not hard to wonder why Nintendo’s R&D1 would make such a change, even with the series in its infancy.
While there doesn’t seem to be any official explanation on record, the commonly-held belief is that it’s due to the extremely limited color palette of the original Game Boy. With only four shades of grey to draw from (filtered through an olive green screen for most of the first several years of its life), differentiating between the growth-inducing Super Mushroom and the extra life palette-swap would probably have been rather difficult at an immediate glance.
The 1-Up Heart would return in 1992’s Super Mario Land 2: 6 Golden Coins with new pixel art, and would be redesigned once again for Donkey Kong in 1994 with a very blatant “1UP” across its surface, leaving little doubt as to what this item’s function could be.
While hearts would continue to appear in Mario games in various capacities (mostly to refill health), their use as extra lives more or less ended as the transition to color titles meant that their distinction was no longer necessary.