One of my eggplant seedlings has three cotyledons or seed leaves. I’ve found extra seed leaves on my vegetable plants before, but only on cabbage family seedlings (see previous posts Seed Coats, Seed Leaves, True Leaves, & Mutant Kale and Mutant Mustard).
eggplant ‘ichiban’ seedling with three cotyledons (seed leaves)
The first post linked to above has additional information about seed leaves and tricotyledons.
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What was the end result with this eggplant plant?
It wasn’t appreciably different from any of the other eggplant.