It seems the compost I used was more lively than anticipated. There's an earthworm crawling around in there.
It's a decent 12 inch pot, but it's still effectively a limited environment. So I'm not sure if I should leave him in or take him out.
UPDATE: alright. I'll keep him in, cross my fingers, and hope I've pulled in enough of an ecosystem to both sustain him for his expected lifespan, and safely handle the subsequent death and decomposition.
On a re-read of the post, I don't see it stated either way. While I've definitely made an unwarranted assumption of it being outdoors now you bring it up, I don't think it's definitely indoors either. The textile in the background of the picture is the only real clue I'm seeing, and even that could be the back of some patio furniture. Lighting maybe artificial...
I don't know if earthworms have some reproduction-limiting mechanism for restricted ecosystems. I doubt it, frankly. I don't think there'd be any problems for the plant, but the worms would probably eat themselves to death within a year or so.
It's an indoors office plant. If it ends up leaving the pot, it'll likely end up getting rolled over by some chair wheels.
Given the soil mix I used, it'll likely be very happy for the rest of its life.