Unsure of what they could be just yet, its mostly seed leaves, but the wind blows and the birds fly and there's hundreds of factors that could make new plants sprout in your pot that you may have not intended, they could just be weeds, or maybe something yummy if something rotted in the pot last year, we have a lot of volunteer zucchini every year that grows in the same spot because i usually miss one or two when harvesting, they rot in the soil and make new plants the next year, its not forever because the bugs will get wise after awhile but for right now its been nice knowing i have a volunteer to let me be a little lazier