Are these plants inside or outside?

If your potting soil is stored outside in contact with the ground, that's probably where the worms came from. If you happened to repot while they were still unhatched eggs, that may be why you didn't see any at that time. Earthworms eat decaying organic matter, so would have no effect on your plants except that they can cause the mix to turn to mud much more quickly. When that happens, the roots of your plants could suffer.

FLYING WORMS!...or at least that's what my mother would say. :)
You might want to eventually repot with some sterilized new soil (cook in oven at 180-200 degrees for about half an hour to an hour, then cool and use). I'd get sick of worms turning up everywhere...and in the carpet...EW. Worms are great, but outside in the garden, where they belong in the universe, and not in my house...unless they're for fishing.

Yes I sterilize my soil by baking it in the oven. There is all kinds of crawlies in soil!

Any critter that needs air will evacuate a pot if submerged. The next time your plant is thirsty, submerging the pot for about 15 minutes should cause anything in there to come out. Might be a good middle-ground for some people.

Tried not to, but I'm too curious to not ask why the worms would evacuate your pot so drastically, Orangeleaves. Did the water have fertilizer in it? When I repot in the spring, plants that have been inside for a few months often have worms in the pots, but I've never found a dead one on the floor, or seen them evacuate pots when I water. (I don't use fertilizer inside.)

I'm not for or against having them in a pot, and hope those who don't want them can evict them, but daggone curious.

There's no right or wrong way to do this, but I have to say I think it's amusing that the people who seem to more strenuously object to worms in the soil of a potted plant would be willing to put dirt and worms in their oven. Interesting. Worms in a pot don't bother me, but the thought of killing them (or any other critters) in the oven grosses me out, and I worry what kind of smell it would make. I'm sure it would do the job of killing whatever lives though.

Was the worm ID'd???

Orange, what color is the worm? From the photo it looks brown-ish, red.

Purple, certain cultures eat insects.
Years ago, an acqaintance offered me chocolate covered cockroaches. I almost puked. 'Um, no thanks.'

Wonder if insects are fried, baked, nuked or all of the above.

PS. Don't know if this is fact or fiction. I've heard soldiers were so hungry during Pearl Harbor Attack, they resorted to eating bugs.