His name is a portmanteau of "hard hat" and "walnut."
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Hard-nut's rough exterior belies his soft, squishy insides. "I don't whistle at the Sunflowers, like some other plants," he says gruffly, scratching his belly against a nearby post. "It's disrespectful and objectifying. Also I can't whistle."
- His design was simply a Wall-nut in a builder suit.
- Despite his description saying it is stronger because he has a "hard, crunchy" shell rather than the Wall-nut's "chewy" one, their shells had the same health. His health was higher because of his hard hat, giving him two additional degrades.
- This also made him the first plant in the whole series with headwear that protected the plant.
- He could resist a smash from a Weightlifter Zombie. It would trigger the first degrade, but the next bite of any zombie will make him trigger his final degrade. This may have been a glitch. Only a Gargantuar Zombie could instantly kill him.
- When zombies ate him, they also ate the builders suit with him.
- When the player won a level with a damaged Hard-nut, he would look undamaged at the end of the level. The same goes for Wall-nut and other knocked out plants.