What is this on my toadstool?

[The_Barrs_Reef]

I thought it was a slug or snail but then looked closed and the polyps are coming out of it.

 

[Tahoe61]

Barnacle, can not say I have ever seen one on a Toadstool. Cool, I wouldn't intervene.

 

[The_Barrs_Reef]

.

 

[The_Barrs_Reef]

Barnacle, can not say I have ever seen one on a Toadstool. Cool, I wouldn't intervene.

Thank you! Anything to be worried about?

 

[Tahoe61]

No.