Please ID this hitchhiker

[smilodon]

I got this one from the LR, they are tiny when I discovered them on the LR, after 2 monthes later, they become bigger than a dime.
what are those?

and what is this? I always saw it being sold at LFS

 

[650-IS350]

bottom polyp....

 

[killingseed2000]

+1...

 

[Supreme Reefs]

beware... the yellow one grows like crazy!

 

[650-IS350]

envasive growers, I never let those things grown on my main rocks.