Once before I started having a vegetable garden, a yellow pear tomato plant came up on its own among some flowers. Now that I have a vegetable garden, volunteer tomato plants come up like weeds.
I pull them out where they will be troublesome and try to keep a few. They are the most prolific drought-tolerant disease resistant plants. They always are the small cherry variety, but one of my volunteer plants this summer has a big tomato on it. I am waiting for it to ripen so that I can figure out what type it is.