Weird hitchhiker growing on rock

[MDReefguy]

Anyone have any idea what these little things growing on one my rocks is? Don't even know what to google to try and research. Looks like they maybe have tentacles? Doesn't look like aptasia. There are a few small ones growing as well.

Thanks in Advance!

 

[MDReefguy]

The little ones look like oval whitish star polyps or something. Better photos under better lighting attached.

 

[EeyoreIsMySpiritAnimal]

Look up "hidden cup coral"

 

[MDReefguy]

Look up "hidden cup coral"

Yep, that might just be it. Safe to keep it seems? Have like 3 or 4 really small ones.