With only the pic above to go on, it sure looks like this to me:
No idea how it would suddenly show up in your pot if you haven't had it around before. A chunk falling into the pot could take root easily, but it would have to fall from somewhere. I don't think I had the variegated form yet when we traded plants, so it couldn't have come from me, (but I did have the non-variegated type at that time.)
Variegated Tradescantia fluminensis would be my 2nd guess. When you get a minute, try getting a pic from a diff angle? (Which looks kind of tough, it's pretty short, huh?) Maybe put a common object in the pic for scale? This is a fun one!
