. . . I just noticed this one today growing in a pot containing a single coleus that's been on my porch all summer. Are these elephant ears, or something else that resembles them? Many thanks for help and suggestions!

Yes, they seem to be alocasias or colocasias.

Will grow from seed, too. Maybe a couple came along for a ride from somewhere else. Nice bonus, though

Thank you triniguy and alisonoz. I figured that's what they were but just couldn't figure out where they came from. They're unlike any of the other elephant ears I have here. Nice bonus, indeed! Thanks again.

They look like Alocasia reginula. You need to be careful they don't stay too wet. They're far more susceptible to over watering than most other Alocasia.

Tropic nailed it!

Alocasia reginula
Also known as black velvet...

They are finicky! Easy on the water, and sun! No intense full sun!

You should feel rather lucky...I've been searching for that EE for some time!
They are easy to find online, but because of their nature to go dormant when stressed, and the fact that online sales usually net me a tiny plant, I've avoided ordering one and have been searching locally... No dice!

Good luck with it!
If you end with a bunch of em by next spring, I'd happily trade you a handful of other EE for a healthy black velvet...

Thank you tropicbreezent and grabmebymyhandle! I do tend to overwater, which is one of the reasons I have so many hostas, ferns, and elephant ears in well draining pots. They'll generally take my well-meaning attempts at love. I'll be sure to be more careful with the black velvet. And no worries about too much sun -- both pots are in bright shade with no direct sun at all.

I'd be up for a trade next spring, grabmebythehand. I'd need some schooling in the best way to prepare and ship it, though . . .