Mystery booger on coral

[karlandtanya]

Saw this thing on a coral today; it came off easily with a toothbrush (just used the bristles to pick it off & trap it--not to scrub the coral!). Maybe 10mm long when it's all spread out; 1/3 that when I first took it off of the coral.
Here it is while attached on the coral:

Here it is after I put it in a dish by itself & let it spread out again

Kinda reminds me of the neural parasites in ST:TOS "Operation Annihilate!" Hopefully I don't wake up with one stuck to my back...

 

[Lovemyreef2015]

Looks like a type of polyclad flatworm to me. I would keep an eye out for more. Remove all that you see.

 

[karlandtanya]

OK, thanks for your help; I will keep an eye out!
The coral didn't look damaged after I took it off. I couldn't tell where it had been once it was gone.