What are these

[xXAXELXx21]

Hello everyone, I'm new to reefing and just noticed these worm like thing coming in and out of the rocks. Can someone ID them and tell me if they are good/bad and if so how can I remove them?
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[Downbeach]

Miniature serpent stars...good neighbors.

 

[Knapp870]

+1 yep, part of your cleanup crew that hitchike in on stuff.